For security reason since VPN is not all about bypassing restrictions, but because of many abuse happened for example multi accounting and bypassing restrictions the casino flagged some users that's why some people encounter an issue with it.
That's why as much as we can we should avoid using VPN. If they think they are not in comfortable places better not to gamble, they could just do it when they think everything is fine and they don't need to worry about their safety. Also other should not think about bypassing a restriction since for sure the casino have ways to detect their actions done.
If the casino allows VPN, you can use it if you don't do any multi accounting activities on their platform. You use VPN that is allowed and you don't break any rule of their ToS without multi-acounting activities so you don't have to worry that VPN usage will be used as a reason against your account and its fund.
Ony people who abuse ToS via the VPN usage for multi-accouting to exploit the casino, will be detected and punished. It's clear that the casino does not only rely on their detection on user IP addresses, VPN usage for their conclusion of multi accounting and related action against users. Before they accuse a user does break their ToS with multi-accounting, they would have collected enough evidence that exceeds VPN usage.
By this universal decision making process in gambling industry, when a casion took action against a user with multi account reason, there is almost no chance for appealing successfully.