I might have figured out what is causing the doubled exposure time.  I made a new script that is a "minimum viable product" to take exposures, but performs all of the configuration in the way it is normally done in my program.  Doing this I could quickly change various settings to see how the program would react.  I found that I could not consistently get the doubled exposure until I was taking 9 second exposures.  8 seconds and below, it might happen rarely, but at 9 seconds it happened fairly often.

This is my MVP test script:
github.com/aaronwmorris/indi-allsky/blob...ting/exposureTest.py

My indi code (which is based on Marco Gulino's indi-light-tools) has a synchronous mode for taking exposures.  Basically, it sets the exposure value and then queries the status of the exposure control until it is idle.  The code I was using would query the status of the control every 0.05 seconds, or 20 times a second.  Backing off to 0.15 seconds between status calls seems to do better.  It appears the cause of the doubled exposure is aggressively querying of the status of the exposure control.  I am not sure if it is the total number of status calls or just the calls-per-second causing the behavior.

It does appear to be specific to the sv305.  I have tested several other cameras (ASI, QHY) and they do not exhibit the same behavior.

This is the code where my script queries the status:
github.com/aaronwmorris/indi-allsky/blob...exposureTest.py#L352

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