USPS module not firing 1 out of 10 times

I’m the admin for a site that uses the commerce_usps module and it is failing to fire approx. 1 out of 10 times. I’ve checked the log files and am not seeing any errors or weirdness re: the module. to be clear, some orders are being processed without adding any shipping charges whatsoever.

i’m using version 7.x-2.x-dev but have noticed there is a more recent date on the module although the version number is the same...?
shouldn’t have a newer version number?

is there anyone else having intermittent problems with this module?