For me it smells like an scam too... Maybe some people make a depo trying to exploit the bug reported by OP, but that's the right way to lose the money.
I just take a look to trust pilot and there are some reports for that site...
https://www.trustpilot.com/review/www.betvision.com
Scam website! Attached to stake.uk which is also a scam website! As soon as you win money they’ll instantly block your account without giving you a valid reason, they’ll then ask for loads of documentation over and over they want to know absolutely everything about you and your life!! Disgusting casino.
Absolute thieves.
I will NOT be removing my review until I’m PAID IN FULL!
I did a welcome offer with this lot. Never bothered again until one day I was checking my list of bookies to see what funds I had in each and when I tried to log in, a message came up saying my account had been closed. Why? Because I then realised that this cowboy outfit are part of FUN88 and TLCBet and I had the nerve to withdraw my funds from both of those 2 joke sites.
Another crap scum bookmaker that never hand out free offers or bonuses.
Avoid.
So, be careful guys and don't deposit on this site, you will risk your money if you decide to try this bug.