Troubleshoot potential REX fix bug

[ericpassmore]

Transferred from AntelopeIO/reference-contracts#6 original author stephenpdeos

There are reports in telegram and internally that the REX fix bug we believed to have resolved with the 3.1 release has an issue.

Original report of issue: https://t.me/Mandel_LaunchGroup/1346

Context from release notes:
This release includes a backport of EOSIO/eosio.system#54 (originally authored by @deckb) which works around the REX rounding bug that stopped accounts from selling REX.

Accounts may now use the voteupdate action to restore their account.

In addition, the bug has been fixed so it does not impact more accounts in the future.

We need to:

• Verify whether we can unlock funds from REX with voteupdate
• Recommend whether we need DevRel to incorporate more thorough documentation for this process