I've been having similar issues with tabular forms giving the following error when validations fail (or I use apex_error):
ORA-20001: Error fetching column value: ORA-01403: no data found
The reason that I initially experienced the error was that I created a bespoke tabular form process to "do something" and deleted the ApplyMRU process that was created by default. I subsequently recreated the ApplyMRU process and set it to Conditional=Never - this solved the problem.
I spent nearly a month on this problem. To solve it, I literally restarted from scratch (I think one of my tables was giving my problems as well). When I remade the page, it worked beautifully. I know another person that had to remake the page as well and then only change a thing or two at a time, test, and repeat and it works for her now as well. I'm sorry there isn't a better answer than this.