I recently got a teensy 4.1 from sparkfun. It works sometime, but after a while (few minutes) it stop responding and the board gives me 9 blinks.
If I restart the board after that, I get 4 blinks which seem to point to “ARM JTAG & SWD Not Responding (Needs Crystal)”.
Measuring the signal at C1 (Teensy® 4.1), I do not see the 24 MHz signal when the board is in this state (when the board is in a working state, I clearly get the 24 MHz signal).
Is the Y1 crystal defective?