the rating for most drive errors is about 1 in 13000000000000, give or take. which is becoming 1 drive. so if you run a raid 5 and 1 drive fails, you replace that drive, and while rebuilding a bit error happens it will corrupt that raid. say you have 10 by 10tb raid 5, the chance of an error becomes 1 in 8.
but like i have said before, this is only an issue when the drives are 8,10,12 tbs.
not to said raid 5 is bad in small low TB arrays. a 5 by 2tb would be completely fine.