Fields reverting to old value when updated

[KyleacQuire]

Hello,

Im trying to update a couple of fields - Person Source, Last Touch Medium. In a certainly couple of records there is existing data that I want to change, but when I do change, it doesn't save and reverts back to the original value. In other records I can change and it updates but these particular records it just wont update. Not sure why

[SanfordWhiteman]

Do you see it reverting in the Activity Log? Because that'll also show the reason.

[KyleacQuire]

No, nothing; my change doesn't appear in the activity log either. On other records it updates and changes perfectly fine.

[SanfordWhiteman]

That's pretty strange. Do you have Block Field Updates turned on for this field, and are you 100.00% certain that you are doing the same test for all leads (i.e. changing from empty to filled isn't the same as filled with "a" to filled with "b").