Simple script to see the status of an account in bags-list. Just paste this in Polkadot JS App's Javascript page.

bags.rs

// This must be a STASH account. 
const yourAccount = "xxx";
// This is your node in the bags list. Use `node.prev` and `.next` to see where you are located. 
const node = await api.query.bagsList.listNodes(yourAccount);
// This is the bag to which you belong.
const bagUpper = api.createType("Balance", node.toJSON().bagUpper);
// This is the list of all the bags.
const bagThresholds = api.consts.bagsList.bagThresholds.map((x) => api.createType('Balance', x));
// 
// This function will always indicate that for an account with stake (aka, weight) `w`, to which bag they belong to.
const notionalBagFor = (w) => bagThresholds.find((t) => t.gt(w)) || api.createType('Balance', new BN("18446744073709551615"))

const ctrl = (await api.query.staking.bonded(yourAccount)).unwrap();
const currentWeight = api.createType('Balance', (await api.query.staking.ledger(ctrl)).unwrapOrDefault().active);
// now we can check if you need a rebag or not? 
console.log(`current bag: ${bagUpper.toHuman()}, correct bag: ${notionalBagFor(currentWeight).toHuman()}`);