I will check it when I get back home, but the chip doesn't reset every 10 seconds; it runs stable. However, when connected to the ST-Link, it resets one time after 10 seconds and then runs stable for hours without any further resets.
I've tried this last night;
I had a brand new board, so I soldered some pins on the program header and tried it. Same problem - it resets once after +-10 seconds every time the st-link is connected.
Next, I tried a different programmer. I have a discovery board with an ST-Link, and that works just fine with the air32, no resets. So I thought it must be the programmer, but the programmer works just fine with an STM32H750, STM32FEB, etc.
The discovery board has an older firmware, so I tried the older firmware V2J40S7, but it made no difference.
I ordered two new ST-Links, a V2 and a V2.1, and I also ordered a DAP-link, maybe one of those will work normally.
Update:
Sometimes I'm just stupid, the AIR32F103 is already a DAP-link, and I have a second one, so I already have a working DAP-link. 😅
And I no longer suspect the AIR32F103. The CSK32F103 also had the same problem, but not all clones. I've checked 4 different clones and 3 original STMs, and only those two stopped working correctly last night.
This issue doesn't seem to be specific to AIR32. If I discover any interesting insights or if others encounter the same problem, I may start a new topic.