happens more often than not, have tried 10 different APIs but it still keeps happening. After like 20 goes it eventually works...
Edit: To help anyone still struggling with a similar issue, it was down to having too many accounts. I was able to load up the account page, inspect element and wait for js to load full account list, clicked on keys, exported the private keys for the accounts I cared about and then imported them manually into a new wallet and it works fine now.