“Don’t stop till it’s fixed” is bad advice.
In rehearsal, there can be a strong motivation to stay with a piece or a problem spot until it’s corrected. This is often a mistake for two reasons.
First, because spending additional time on that piece is by definition taking time away from other repertoire or rehearsal work. You may be fixing that problem, but you’re setting other pieces up for struggle later. Better to stick with the plan you had, at least in terms of time.
Second, because work happens after rehearsal. Even if the problem isn’t fixed when you planned to leave it, there will be conscious time (practice) and unconscious time (background processing) done to continue to fix the problem before you next address it.
Have a plan that serves all your musical needs, and then stick to it.