Have had a few issues with one remote out of the two supplied with the car, one remote one press unlocks everything, the other remoteyou have to press the remote twice to unlock everything, can manage this no biggy, the issue now is the car locking itself, you can unlock it start the car drive etc in dry or wet get out shut the drivers dor and on some days the car will lock itself EVEN IF THE KEY FOB IS INSIDE, it caught us out once at a pertol station as both of us got out and doors were shut, had to wait until m daughter brought my spare key fob t get in, it's a kyless start nut not entery, have taken it to dealers no faults showing and thier only solution that the came out with was to replace the whole alarm system,cheeeeeeper to change the car i thinkkkkkkk, just wodered has anyoe ever come accross this problem, just to add fitted new batteries in both remotes car is a 2019 1.0 TSI SE L Estate it's the uplift model from the MK3 but not a MK4

Didi you synchronised both keys?

You could try swapping batteries over in the remotes to see if issue also swaps, plus refitting a battery (fully, properly if not as such previously) might sort this if it's battery fitting related.

Perhaps resetting or recoding the keys to the car. This sounds more central locking or remote issue(s) than alarm.

Best is not to have a spare key as such bout to use both keys/remotes in any rotation/alternating you want, this means the batteries, remotes and metal keyblade get more even wear, you know how the batteries in each are and that they work and where to easily find the key not currently being used.

With these proximity things you want the key not in use kept out of range of the car, in a tin box if required.

I'd be trying anything cheap (free), easy and quick before going to Dealership/garage/mechanic/auto-electrician/locksmith and getting too involved in VW computer systems and programs.

There are threads and posts that have one remote key doing different to the other but I can't remember what outcomes were given, any.

As you have found "no faults showing" doesn't mean there aren't faults, tho' to be fair if the issue is intermittent it can be a lot more difficult to pin down when it's not playing up.