>as I have nearly no expirience with scheduler, consider the following a shot in the dark:
>create a minimal exe for try-catch-creating only a StringToFile(transform(DateTime()),FixedString) log in root of C, curdir(), TempDir and where the exe sits, to check if basic idea is hindered by something in system setup.
>
>prompted by the description that exe runs ok if started from file explorer - until such a test is completed, at least the mind over here would be severly distracted trying to read up/figure out too many possibilities in Windoze

I was considering such an option, i.e. hardcoding a path and sending a log to it, IOW create a specialized exe to at least see where is my exe running, but the solution was far simpler.

I moved it to a different box and now it runs there. Set it up in ten minutes. The downside is that the first box was holding one of the SQL servers that this has to connect, so now it's communicating with both of them at some distance. The upside is that it works, it now simply works just like it does on other twenty-some places. In the balance, the milliseconds lost would take about a decade to be greater in total than the time I lost.