It could be interesting to understand the actual content of the qrcode. part1 is a static id, so likely linked to the membership.

part2 seems to be a timestamp. Maybe we can try to forge the value to "now - 10 seconds".

And if the implementation has been done right, the "part3" should be a signature of part1 and part2, not a "salt" (so forging part2 should be detected and code rejected).