I had the exact same problem with bitsler (but also with Stake, and SportsBet). They always told me that the limit was set by the odd provider. I cannot bet more than 0.2 mBtc on bitsler most of the time (except maybe for premier league main markets). On Stake it is even worse, and for sportsbet they have also lowered my odds. I think it is quite common among casinos ...
I am not sure But I think the odd provider of these three sites is the same. While I see on the gambling (cricket) their design of the cricket page is almost same and decrease of the odd limit is also the same. We have nothing to do if they lower our limit and the customer support team says the same (we have nothing to do type words).