So, I know that this is a subject that's been beaten to death on these forums by now, but everything that I've read (and I've read EVERYTHING here) doesn't seem to be solving my issue.

In our dev org, portal users keep hitting the insufficient access on cross reference id error, which also prevented us from properly testing our portal users in context. Now, before you ask, we're basing our security access on another org that is the foundation of ours.

The cross reference id issue points to the Account object through a Related Account field, but the portal user has ALL necessary object and field access to match that of the org we're following, and the sharing settings match as well (Account set to Private).

The problem is, when trying to view the first page where Account is needed, the portal user gets bumped to an error page and hit with an insufficient privilege issue, and now I'm stuck wondering what else I missed.

-the portal user profile is an exact match
-the sharing settings are a match (no sharing rules at all)
-our role hierarchy is an exact match
-our record types and record type access are an exact match

After all this, I'm honestly wondering what I could be missing. If anyone has further ideas, I'd really appreciate it, as we've been stuck with this issue for weeks, and the only work-around so far was to temprorarily set Accounts to "Public Read/Write", which of course fixed the issue, but we absolutely cannot have that in production.