Quest you get from Silics village, that asks you constuct resource extractors does this weird thing and is never completable - 

it shows for example 0/2, and then if you complete 2 extractors, it will show 2/4, and then if you complete 2 more, it will show 4/6 etc. (seems constructing extractor increases both count and quest requirement the same time)

so it happens always (and the bug has been there for years?)

Thanks for the report, we'll take a look into it