My partner and I both work at the same company and have our 401k with Fidelity NetBenefits. When I add both accounts, the second one will overwrite the first one causing incorrect data for the first account. Is this a known issue in Quicken?
There is an old discussion here about some difficult connecting two separate Fidelity accounts to the same Quicken file that might help:
But I don't think overwriting data would ever happen, unless you are signing in to your wife's account and then linking the already existing accounts for your account to her new ones, which is user error. You should not keep them matched.