Make the cutoff cue clear at rehearsal
A raised hand needs an agreed meaning before it can guide an ending.
Ask the leader how the ending will be cued and what the drums should do on the last beat. Confirm whether the band stops together, holds a chord, or lets a final drum accent ring. A hand movement can mean a repeat, a stop, or something else depending on the band.
Run the last phrase at rehearsal with your chart in place. Find the point where you can look up and still keep your place. If a repeat mark needs too much attention, make it clearer and rehearse that passage again.
Watch the agreed cue and finish the part the band practiced. A missing lyric or raised shoulder alone is not a reliable cutoff instruction. Mark any changed ending before leaving rehearsal, then practice the approach as well as the final hit.