I got data from them and while on Bonus my RTP was over 100% - could not press a button but I won! Ended up with hundreds that of course, I could not withdraw as the Bonus Wagering Requirements were for thousands and so so had to "play it all away" over a few days. Never did quite fulfill the wagering, although I got close. Then IMMEDIATELY my balance returned to 0.00 and the wagering withdrawal restiriction were gone and I deposited more money, my RTP went down to twenty something percent.
Waited a week or so and played other places, then went back. RTPs then averaged somewhere between the 2 extremes above, but after a month or so my RTP was still and way below their adversised rates and I never won enough at one time to make a withdrawal (although once won about £50 and should have withdrwan it - but thought I'd try to win as big as I had when on Bonus and lost it).
Remember - I never actually made a withdrawal all the time I was there.
RTP was still well "below what they would like to see", and so I was given a load of free spins to try to bump it up, which it did slightly - but even then, my overall my RTP just made it to about 80%.
Asked for a "gesture of goodwill " but not forthcoming - and Manager a bit aggresive / overly defensive / accusing me of doubting / questioning the integrity of casino etc - and insiting the RTPs were fine etc. I left.