Hi @netscream
When you use the I2c3, you are using it as master or slave?
Do you check this code?
SDK_2_10_0_EVK-MIMXRT1060\boards\evkmimxrt1060\driver_examples\lpi2c\interrupt
This code use I2C1 as master, I2C3 as slave, if you use the I2C3 as master, you can change the code and test it directly, whether you can reproduce the issues or not? You can change the LPI2C_MASTER_SLAVE_ADDR_7BIT to your own defined data. Please note, this is the 7 bit address, you need to set the data in the range of 7bit.
If you still have issues, just kindly let me know.
Best Regards,
Kerry