Teensy 3.6 Serial6 doesn’t work in conjunction with other ports

[ssilverman]

From an email:

I am trying to use Serial6 for a teensyDMX Sender running on a Teensy 3.6 and can’t seem to get it to work. The other 5 serial outputs work well and I can use those 5 and create a Sender with Serial6. It’s when I call begin on the Serial6 Sender that things break down. I’m not sure what is happening but none of the other serial outputs work after that call. Searching on the Teensy forum I found a message from 2019 where you mention an LPUART issue, could I be running into that? If you haven’t had a chance to test Serial6 on a Teensy 3.6 in the mean time, and are still interested in it, I can run tests and check the outputs on a scope.

More details:

1. Serial6 works by itself.
2. Just Serial6 and Serial1 doesn’t work.