do all three fix errors?

The reporting SOL is 7.5 years from the date of first default so unless that period is over, there is no point disputing.
As for your second question, no, disputing a tradeline with Experian will do nothing to fix errors being reported by other credit bureaus.

I am actually going through something similar to this as we speak....I have an account that was already proven not to be mine showing up on all three of my reports. The account shows as having been originated in 2004 and was always delinquent, even according to the original creditor. There is a third party that also reports this debt. OC reports it as closed in 2006, yet they keep updating the date of removal. What I mean is this--here is what the OC reported on my credit reports three months ago:

date opened: 2004
delinquent the entire time since it was opened
OC lists account as being closed in 2006.
Heres the big one--date the account will come off my report:

October 2019

Now, that was three months ago....as of today, on that same credit report, the date for removal has changed to January 2020. So, every month, they are adding another month to reporting time.

On my second report, they are doing the same thing. On my third report, it is scheduled to drop off at the end of this month. They update all my reports every month.

Now, the third party is following along their reporting, so they are doing the same thing. I put in a call to my attorney today....lets see how this works out.....