As I have never used the Python synchrophasortoolbox package, I cannot provide any insights into that tool.
However, if this occurs again, I would suggest running the PMU Connection Tester to see if it also observes a change in stream behavior, that would identify if the issue resides in the Python package or the openPDC.
If you do find the issue is coming from the openPDC, we would need things like (1) version of openPDC you are using, (2) details on your configuration (like database type, how many and types of synchrophasor devices, etc.), (3) system characteristics, e.g., CPU speed, cores, total memory, and (4) log files.
Thanks,
Ritchie