Negative cost price/gain appearing on a brokerage cash account and incorrect lot balances

Hi - I'm suddenly finding that my brokerage cash balance in the account summary seems to be showing a gain and negative cost price even though all buys and sells are cash at par. Also, even though my cash balance is correct in the account summary, the shares reported in the lots do not add up to the correct balance, so when I try to make a sell entry I get a 'not enough shares to sell' warning.

The gain/negative cost issue seems to start with an entry at the end of November 2025, but the entries at that time look correct as far as I can tell and no different than I usually make. When I delete the entries on that date the issue goes away but when I re-enter them I get the same issue even using a different date. Just wondered if anyone has come across this issue at all and how to correct.