C182 pilot reported an near midair collision with traffic not at ATC reported altitude.

Narrative:

During a practice IFR flight with an instructor to ZZZ; ZZZ center advised of a radar outage beginning roughly halfway to ZZZ and that they would lose radar contact with us. We requested the runway xx RNAV approach and were told to expect that; but to be ready for holding instructions as there were one or two aircraft ahead of us. We were issued instructions to fly the published hold at zzzzz and expect further in 10 minutes. We did the entry to the hold and then went twice around before being cleared for the approach and advised that there was VFR traffic inbound also; then handed off to ZZZ tower. We checked in with tower and were advised that he had an archer holding over ZZZZZ1 (FAF on our approach) at 3;500 ft.; and another aircraft that was VFR who would remain west of the extended centerline to keep clear of our approach. I told him we were looking; but we did not see either at that point. I went head down to hand-fly the approach while my instructor watched outside and kept looking for the two aircraft. As we were nearing ZZZZZ1 and about 100 ft. Above the minimum crossing altitude of 2;800 feet; my instructor said 'ok there's an airplane; we're descending' and pushed on the yoke swiftly; but not aggressively; to avoid collision. I radioed to tower that we were deviating for traffic. He called back; asking who called and what happened; and I advised him that we had nearly hit the archer as it crossed left to right in front of us. We estimated we were around 200 feet below it when paths crossed. The archer then radioed and said he'd had us in sight. We resumed the approach; flew the missed and returned to [departure airport] normally. It is my belief that the archer was holding at 3;000 feet instead of 3;500 feet as the tower had instructed. I don't recall hearing him issue the holding instructions after I switched to tower freq. The radar outage added to the issue; however; I am not sure to what degree it would have helped in this case as I do not know if ZZZ is a radar class D. I felt it necessary to submit this report just to put down thoughts and have on record; but to also highlight that in that situation the tower is relying on pilot reports (I assume) and the chance still exists that an aircraft is not doing as expected or as he thinks he is. Also I wanted to point out the importance having a safety pilot (or instructor in this case during training) when flying IFR in VMC.

Original NASA ASRS Text

Title: C182 pilot reported an NMAC with traffic not at ATC reported altitude.

Narrative: During a practice IFR flight with an instructor to ZZZ; ZZZ Center advised of a radar outage beginning roughly halfway to ZZZ and that they would lose radar contact with us. We requested the Runway XX RNAV approach and were told to expect that; but to be ready for holding instructions as there were one or two aircraft ahead of us. We were issued instructions to fly the published hold at ZZZZZ and expect further in 10 minutes. We did the entry to the hold and then went twice around before being cleared for the approach and advised that there was VFR traffic inbound also; then handed off to ZZZ Tower. We checked in with Tower and were advised that he had an Archer holding over ZZZZZ1 (FAF on our approach) at 3;500 ft.; and another aircraft that was VFR who would remain west of the extended centerline to keep clear of our approach. I told him we were looking; but we did not see either at that point. I went head down to hand-fly the approach while my instructor watched outside and kept looking for the two aircraft. As we were nearing ZZZZZ1 and about 100 ft. above the minimum crossing altitude of 2;800 feet; my instructor said 'OK there's an airplane; we're descending' and pushed on the yoke swiftly; but not aggressively; to avoid collision. I radioed to Tower that we were deviating for traffic. He called back; asking who called and what happened; and I advised him that we had nearly hit the Archer as it crossed left to right in front of us. We estimated we were around 200 feet below it when paths crossed. The Archer then radioed and said he'd had us in sight. We resumed the approach; flew the missed and returned to [departure airport] normally. It is my belief that the Archer was holding at 3;000 feet instead of 3;500 feet as the Tower had instructed. I don't recall hearing him issue the holding instructions after I switched to Tower freq. The radar outage added to the issue; however; I am not sure to what degree it would have helped in this case as I do not know if ZZZ is a radar Class D. I felt it necessary to submit this report just to put down thoughts and have on record; but to also highlight that in that situation the Tower is relying on pilot reports (I assume) and the chance still exists that an aircraft is not doing as expected or as he thinks he is. Also I wanted to point out the importance having a Safety Pilot (or Instructor in this case during training) when flying IFR in VMC.

Data retrieved from NASA's ASRS site and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.

Attributes
ACN	1587431
Time
Date	201810
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.Airport
State Reference	US
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	Cessna Single Piston Undifferentiated or Other Model
Operating Under FAR Part	Part 91
Flight Phase	Initial Approach
Route In Use	STAR JAGGR THREE
Flight Plan	IFR
Aircraft 2
Make Model Name	Piper Single Undifferentiated or Other Model
Operating Under FAR Part	Part 91
Flight Plan	VFR
Person 1
Function	Pilot Flying Single Pilot
Qualification	Flight Crew Private
Experience	Flight Crew Last 90 Days 32 Flight Crew Total 165 Flight Crew Type 32
Events
Anomaly	Conflict NMAC
Miss Distance	Horizontal 200 Vertical 150