Hello IristoId.
Many thanks fro your feedback... Sorry for the late reply I was out tocuhing grass :)
I was trying to replicate your bug but I did not succed... I can upload many 6 sprites strip with no problem and even mix some different sprites and still keeps building... 
Maybe I do not understand your bug. If u still find this bug let me know... Intereted on crush on it :)
Thanks :)