Thanks, that works perfectly. I'm handling the hook in my custom theme, but this probably needs to be in the https://community.nodebb.org/post/95161 plugin as well (without the importedVotes)
library.setTopicVotes = async function(hookData) {
const topicData = await topics.getTopicFields(hookData.post.tid, ['cid', 'importedVotes']);
const importedVotes = topicData.importedVotes || 0
const voteData = await db.getSortedSetRangeByScoreWithScores(`tid:${hookData.post.tid}:posts:votes`, 0, -1, 1, '+inf');
let allvotes = voteData.reduce((acc, cur) => acc + cur.score, 0);
allvotes = allvotes + importedVotes
await db.sortedSetAdd(`cid:${topicData.cid}:tids:votes`, allvotes, hookData.post.tid)
}