One of the problems i just fixed by looking at another thread, it was about mario 3 backgrounds having a block limit and getting glitchy the higher you go.
The second one is still persisting, and all of the proposed solutions for it have already been done, I'm not sure what else to try. Thread on it is already here:
http://www.supermariobrosx.org/forums/v ... =35&t=1351
I just wanted to try reinstalling SMBX just to see if anything happens? I'm fairly new to using the editor myself, but I've been playing it for about a year.