Uplink Frame Count equal one not working after reset

Hello everyone

I am using ABP and I reset the uController after every frame I send (standby mode of the uController is equal to a reset).
This means, at the moment the uC always starts with a Framecount of 1.
For this setup I enabled the box “Resets Frame Counters” on TTN (v3.13.3) for the specific device.

Now I have a very strange behavior:
When the Uplink Frame Count is equal to 1, the Frame is not received.
But if I have sent some more frames the last time I had the node running (eg. Uplink Frame Count was 5), the Uplink Frame Count is reset to 1 and the data is received clean.
Also if the frame was not received, the second one will be (makes sense since the counters are than in sync)

Can anyone explain this behavior? Or could it even be a bug from TTN side?

PS: I know this setup is not recommended at all (ABP, resets Frame Counters), but for first development with Standby, I thought it is the easiest way.

Thanks for your answers :smiley: