Event Balance is $0 but Contribution side thinks a Refund is owed

Not sure if this is a regression [this is 4.7.27] or if it has always been an issue - but switching a participant from one session -> to another -> produced:

• Event Balance: $0 (which is correct)
• Contribution Status: automatically switched to Pending refund (which is not correct; status is locked: can not be correct to completed;

So the math here is wrong -> hence the conclusion: Pending Refund is wrong;

Client has no access to phpMyAdmin and or any other backend tools - this scenario is created purely via the GUI;

I'm going to try and reproduce this in a more standard environment - but wanted to file this issue to give people a heads up;