regex in Liferay Forms is not working as expected

• Type: Bug
• Status: Closed
• Resolution: Fixed
• Affects Version/s: 7.1.0 CE GA1, 7.1.10 DXP FP1, 7.1.X, Master
• Fix Version/s: 7.1.10 DXP FP10, 7.1.10.2 SP2, 7.1.3 CE GA4, 7.1.X, Master
• Component/s: Forms
• Labels:
  • QA-V
  • ee-ts
  • fw_test_unit
  • liferay-dxp-71-sp2
  • liferay-fixpack-dxp-10-7110
• Branch Version/s:
  7.1.x
• Backported to Branch:
  Committed
• Story Points: 0.25
• Fix Priority: 4
• Sprint: F&W Sprint 9
• Git Pull Request: https://github.com/brianchandotcom/liferay-portal/pull/64802

While trying to add a validation on a text field I ran into the following error message while saving the form

New Form is temporarily unavailable.

I was using 'If input does not match' with a regex like:

\d+

OR

\d{10}

Since this is a regular regex I expect this to work.
My workaround for now, trying to validate on numbers was to use

[0-9]{10}

But this really should work with all kinds of regex, simple and advanced.