Set built the timetable with *x = append(*x, ts), so setting a bandwidth
timetable on a value that already held one kept both schedules. The single-value
branch of the same function has always done *x = BwTimetable{ts}, and the other
multi-token Set methods in this package build into a local and assign at the end.
The visible effect is through the rc API. The "main" options block registered in
fs.RegisterGlobalOptions is the live globalConfig, and options/set reshapes JSON
straight into it, so
rclone rc options/set --json '{"main": {"BwLimit": "Mon-10:00,1Mi"}}'
added to the running daemon's timetable rather than replacing it, and the older
slot kept winning: LimitAt for a Sunday returned the previous 10Mi. The same
applies to a _config override on a single call, since AddConfig shallow-copies
the global.
Building into a local also stops a failed parse from leaving the previous
timetable partly overwritten, which the existing error cases already expect.