Any type of software timed commands like SERIN/OUT, OWIN/OUT, PAUSE, PULSIN/OUT etc, will be disturbed by these types of Interrupts.

Since you have 4 different things interrupting, the software timing is getting messed up pretty bad.

If you only needed the transmit side, you could use ...

Tmr_tx-18
http://www.picbasic.co.uk/forum/show...1&postcount=28

But it sounds like you need the RX side too.

With a need for 3 USART's, You may be out of luck.