I have just created a Modbus serial data source using ttyS129, which is a symbolic link pointing to ttyR00.
I am using Moxa NPort 5150 Ethernet Serial modules and they create virtual devices ttyR00, ttyR01, etc.
Since RXTX seems not to enumerate them, a symbolic link is a quick workaround.
When I create a new source the serial port indeed shows up and all is good (I can communicate).
When I look at the list of data sources it is also all good (data_sources.shtm) and the source shows up wity ttyS129, also when I export I get it right.
But when I click on edit, I am left with only ttyS0 and ttyS1.
When I edit the data source, I only get ttyS00 and ttyS01 in the HTML form (data_source_edit.shtm?dsid=31)
Exporting, deleting and reimporting with the corrected ttyS129 seems to have fixed my problem.