Thanks for looking into my logs and clarifying what’s happening.
CPU is powerfull enough and it is not overheating. The problem turned out to be macro M106. With cooling turned off no errors appeared during test prints. I copied someone else’s code for IDEX without much attention to its code. After replacing it with a simpler macro from here, the problem disappeared.
I’m a little surprised I’m the first one to encounter such issues. There is no official example of M106 configuration for multi-extruder printers, so everyone writes their own macros and, as it turns out, some of them are too stressful, especially in combination with adaptive cooling, when the slicer issues a lot of these commands in a short period of time.
I suggest adding computationally expensive macros with lots of conditions and variable accesses to the list of potential causes for this “Timer too close” error