I switched the two Moths & GPS units on and off a number of times while in the open and removed the battery in between. That way the GPS turned on each time to set the clock. One of the two units has now corrected itself, the second should not take much longer. No need for an extra firmware. Thank you for the super-fast help to track down this issue. Fantastic service. And by the way: is there a place to suggest features for the Audiomoth-config app?

ok, that would be great.

The two affected are from a batch received by Andy (only GPS). All modules basically look the same. Do you think the issue would resolve if I just keep them running for a few more days in a location with good GPS reception?

It turns out that the issue is really connected to individual GPS modules. This is what the test last night produced: It seems that the 2s offset is indeed coming from the GPS modules. I would think that they can be programmed somehow to do this?

All Audiomoths have Firmware 1.8. There are actually two different types of GPS modules in use here: 8 modules received via Andy in April on Moths M22 to M29 (these are GPS only) and 4 via the latest Groupgets campaign on Moths 01n to 04n (GPS+Glonass). I had the Moths running overnight and changed GPS modules. Will see if that makes a difference.

MFH is a manufacturer of waterproof plastic boxes (ie with rubber seal). The small ones go for less than 3 Euro if you search around. We use almost 40 of these, without a failure so far.