moving map severe glitching in flight

[Seagull]

I just did a 20 hr CC flight. During the flight my moving map started glitching. The glitch would progress over 15 minutes until the screen was tumbling and be unusable. When I landed for fuel, 10 minute stop, then restarted the screen would be OK for 2 hours before acting up again. When I got to my destination I found a loose connector and tightened it, test flew and no glitch. On the way home it returned. There is a relationship to vibration, idling the engine in flight will clear it up until power is resumed. The glitch will get so severe the map starts tumbling and jumps around, the airplane icon turns into a question mark and the message in the pic shows up.
Attached are a few videos.

Anyone have suggestions on where to start looking for the cause?

 

[swatson999]

Bad GPS antenna, perhaps?

 

[airguy]

Seems likely to be a problem with the GPS. Antenna, cable or connector.

 

[maartenversteeg]

There is certainly something strange going on with the GPS, while flying at 7700 feet you wouldn't expect that the visible GSP satellites change that much over such a short time span. There seem to be GPS satellites appearing and disappearing in the third video, you wouldn't expect such a behavior at such a short timescale unless there are GPS interruptions planned or announced. The system itself seems to continue working and if the cable or connection betweenGPS received and Dynon display was failing then I would think that the status wouldn't continue to report (the reporting seems to be intact although the reported visible satellites change more than I would expect

 

[Seagull]

Update: Testing on the ground. I am using the satellite screen to determine proper operation. I lightly tapped on the GPS antenna mount and the number of "green" satellites would drop significantly. I removed the GPS antenna from its mount and cradled it in my hand with a clear view of the sky. Tapping the antenna now caused no drop in signals but tapping in the area of the mount and on the firewall would cause a drop. I believe the antenna is not the problem. I checked the wiring from the antenna to where it goes through the firewall and saw nothing unusual and saw no signal loss when moving it around. I reinstalled the antenna on its mount and could not recreate the loss of signal no matter where I tapped. I performed 2 flights of .5 hr each, GPS worked flawless, it must have fixed itself .... not!

 

[jakej]

One possibility is too much ‘handling’ of the antenna cable out of the base of the antenna caused your issues - I have seen this before , rarely, & posted about that recently.
my solution - cut the cable (the weight of it can cause stress where it’s potted into the antenna) off about 1ft from the antenna & use a lightweight connector eg 9 pin dsub ( without backshells) or just use the pins & sockets with heatshrink to join later. YMMV.