I may have a similar issue
I recently installed a pair of G5's and there is about a 60' difference between the altimeter and the G5.
I'm planning to fly tomorrow to a different airport so I'll have another datapoint.
OP, thanks for posting this.
Edit: Didn't realize this was a 2 year old thread until after I posted.
Last edited by Mile High Relic : 05-17-2022 at 11:01 PM.
Reason: Old thread