Looks like Paul has fixed some issues with the SD card on Teensy 3.5 & 3.6 in the latest Teensyduino 1.35 beta #2: Teensyduino 1.35 Beta #2
I’m not sure if they’re related to your issue, but it might be worth updating and trying it out.
Looks like Paul has fixed some issues with the SD card on Teensy 3.5 & 3.6 in the latest Teensyduino 1.35 beta #2: Teensyduino 1.35 Beta #2
I’m not sure if they’re related to your issue, but it might be worth updating and trying it out.