thanks for the report @James_Wong 
i’ve reworked the way likes & reactions are counted and synchronized using batches so that it takes a little bit longer in practice but never blocks any major tables
FIX: Recalculate like counters with one shared rule by ZogStriP · Pull Request #44647 · discourse/discourse · GitHub
FIX: Stop the reactions like sync from re-trashing likes every hour by ZogStriP · Pull Request #44648 · discourse/discourse · GitHub