The problem still persisted even after 1.6.2 but I solved it recently. I deleted everything in browser storage inspector related to this website (cookies, indexed database, local storage, session storage and cache storage) and refreshed. I never had to do such thing, whis is why it never occured to me until few days ago.
Also please check stage C. It works as it should when you have only pixels and poxels, but gets weird later on.
I keep losing HP even though I have 600+ extra idle hitters and more than 3.7% instakill chance (and bunch of other skillmine bonuses). On stage C screen I see that I am destroying blocks as soon as they appear, but I keep losing HP as if some invisible blocks are getting through.
Also (this is minor thing) on stage selection screen all stages have working indicators how far are you at the current level of the stage except stage C (it shows layers 0/X, it is stuck at 0, when it should show what is shown on stage C screen, which is current number of destroyed blocks/number of blocks required to destroy to get to next level).