Do you know what transfer switch you have?? There was a period of time that Monaco was installing a Iota transfer switch that had a high rate of failure and there was a recall on.
Iota ITS-50R Automatic Transfer Switch
Monaco stopped installing these in Sept 2001.
After that they installed a Lyght, which is a better switch.
Robot Check
From what I've reat the Iota switches would get hot and melt the contacts and sometimes cause fires. If you have one of these I would replace.
If you have a different brand you may try disconnecting the power, take the cover off and see if you can see any problems. Normally the generator takes priority, so when you shut the generator off it may have not switched back to shore. Make sure if you have Auto Generator Start it is disabled.