This page is intended to show the outline of the chip and to provide additional information that might not be clear from the data sheet.
There is a bug in the chip : When you configure the second UART, the timer1 channel B will not work.
This info came from microchip :
Yes, your observation is correct. It is a known device bug. We already
report this bug to our concern team.
This is due to the fact that timer 1 channel B is shared with XCK1 pin
Usually this functionality should take priority over timer 1 channel B
only when UART is configured in Synchronous mode but after discussing
with our internal team confirmed that timer 1 channel B is
disconnected based on UART1 activation
No matter even if the UART is configured in Asynchronous mode(in which
case there is no use of XCK1) timer 1 channel B still gets disconnected.
This issue also presents in UART2 XCK2/OC2A.