We have had this reported before, however it is unknown if our suggestions actually resolved the problem, as we did not here back...we can only assume.

We do know that in at least that reported case, the full error was:

PCL XL error
Subsystem: TXT
Error: InternalError 0x50
Operator: ReadChar
Position: 760

They were using an HP 4050 LaserJet printer with a PCL6 driver installed.

Since this sounds so similar, I would suggest installing and using the PCL5 emulation, rather than the PCL6. There are no known issues with PCL5.

Some printer drivers do not support MICR. This sounds like one of them.

Please let us know if this helps!

Regards