Something is causing the recording of an extremely short 128 sample loop. The script is running, it starts recording, then immediately on the next audio block it runs again, closes the loop and goes into Overdub mode. Best guess is it is getting spammed by whatever MIDI event causes that script to run. Bring up Help->MIDI Monitor and watch the messages as you go through your reproduction. If this window starts filling up with the same event over and over, then there is something upstream causing problems with MIDI. If the window doesn't have anything unusual in it, then it is something internal to Mobius that is calling this script over and over.
You said software instrument, so that suggests you're using the plugin in a host. Which host, what other plugins are running, etc.
This could also be "event doubling" which is something that can happen when you are running under a host, and you have the host sending MIDI into Mobius and at the same time have Mobius opening a direct connection to the MIDI device that the host is using. Mobius will receive the MIDI event twice, once from the host and once from the hardware, you would also see this in the MIDI Monitor. Usually, two applications can't create a connection to a MIDI interface at the same time, so either Mobius or the host would fail the connection. But a few allow "multi client" connections, if you're using virtual MIDI like Bome, that would allow it.