How can I determine why my balance has dropped substantially

"I have mine set to withdraw automatically every Monday, do you maybe have that too?"
A: if you mean withdraw to an external bank account, No, I only ever do that manually and it's very occasional.
I've double checked and:
Account History shows no withdrawals in the last 10 days
Auto Withdrawal shows 'Nothing Selected' for day of week or day of month. (Shouldn't be, as I've never used that function)


"Does your account history for the last few days show that, or anything unusual?"
A: not that I can see, hence my reason for posting.  I would have guessed that a drop of the order of £450+ would be easy to spot, but I can't see it.

I rang RS, spoke to a guy called Chris, explained my account seemed to have suffered an unexpected loss of £450+ (plus I'd had a drop of around £200 over the last week). He said it MAY be a problem they'd seen recently where Contracts were formed, even had the Lender's name set, but the Contract wasn't linked correctly to the Lender's account, hence didn't show in the account totals.  They're still looking into that (no fix date promised) and would link my case to that 'ticket'. 

For now, I'll sit tight.

When he asked 'is there anything else I can help you with today ?', I said 'you could get rid of that annoying pop-up seen on login, as it's hacking off loads of people'. Got the impression they were aware of lender feedback.

I've just checked my balance and all the missing money from my account since Friday has now reappeared.
Yes I had phoned RS about it this morning - and no I wasn't the only one affected.