My husband's work history didn't get us any points (non-Canadian), but we put it in 'Work History' so he had to get letters anyway. One of the letters came back and he had apparently had the dates of employment completely wrong. Off by about 6 months. Can I just explain that in the LOE and change it on the PR application and have it be okay? Since we didn't get points for it anyway nothing really changes, but I know you aren't supposed to change work history after getting an ITA. Will it be a problem?
Since you are not claiming any points for that experience, remove it from Work History section and put it in the Personal History section. This way, you will not need to bother about supporting any letters. Yes, you can do that post ITA and edit the work experience as long as your CRS points don't fall below the cut-off threshold. Good Luck!