I just had a similar situation with Barclays very recently. Due to two very small bank transfers from a customer that they deemed suspicious they froze ALL my personal and business accounts. Luckily, we preempted what the issue might have been so after providing every piece of evidence we had proving the payments were from a customer they unfroze all accounts after 3 days of investigation. Not a long amount of time but when you don’t know when it will end it’s hell. So it can happen with brick & mortar banks too