@kersing, transpires that LMIC does trigger an uplink to confirm a downlink in v4. Took a while to trace so I’ll not do that with older versions.
I have created an ATmega4808 + RFM95 device specifically to trace MAC commands from TTS as they do appear to be numerous and I can put plenty of debug in to LMIC to see what’s going on, but printf only works (easily) on AVR, not SAMD.
Don’t know how the OP got in to a loop, but my client found the loop-da-loop by sending a confirmed reboot downlink and with the MKR WAN which you know I love, you can’t be sure you’ve done a Tx so if you get a confirmed downlink requesting it you’d then have to send a confirmed uplink to clear the confirmed downlink with the uplink being confirmed so you know that the downlink was confirmed (excepting MKR WAN doesn’t tell you an uplink was confirmed in current firmware) - we’ll end up with two Tx’s from the gateway in short order. What a mess!