On the assumption that there's a complicated control algorithm which, unfortunately, does arithmetic on (now-then) tick-values everywhere... but this algorithm

On the assumption that there's a complicated control algorithm which, unfortunately, does arithmetic on (now-then) tick-values everywhere... but this algorithm has been extensively validated to be correct on the non-overflowing case, and it will take a while to find out how it handles discontinuities in its time scale. Then the simple "raise service-needed signal" would be a valid workaround and easily testable local change for the next two years until the extensively fixed-algorithm went through testing and certification.