Looking at the logic now. It does not appear to stop reading after a comm err. It continues to read the input and if it found the RMC sentence in a subsequent message it would update the dialog with the nav info found.
The Spike software does expect the RMC string to be sent in each update, and it does expect roughly a 1 second update rate. My COM reads have a 50ms readintervalTimeout, and a 2second total timeout. I read 2k bytes at a time in a loop. If you are using a low baud, like 9600, you might simply be trying to transmit too much data in this interval. Consider increasing your baud rate or decreasing your message size if you can.
If RMC messages were still coming in periodically, I would expect you to see it flip between valid and Comm Error.
Looking at the code here, it also looks like it will still save the last lat/lon it found. So even if it was flipping between valid data and comm err, the mapping mode should still be able to query the last valid value seen.
Andrew
