Hey, hey, let's not toss around scurrilous accusations about my favorite controller. Only some CPUs with specific firmware revisions are affected by the issue you mentioned.
Versions 16.03, 16.04, and 16.20 firmware in 1756-L55 and 1794-L34 controllers suffers from the incorrect background checksum fault. This is similar to the issue in versions 15.03 and 15.04 (and 15.05 for the 1794-L34).
This does not affect the 1756-L6 controllers or 1769-L3x controllers and it's fixed in the 1756-L55 in version 16.21 and 15.05 (15.06 for the 1794-L34).
RA Knowledgebase article 45709 and 34430 contain details from the gloomy days of 2007, when controllers were faulting and a pall hung dark over the land, as paladins of Technical Support roamed astride their minivans, armed only with CompactFlash and a will of steel.