Taxonomy field with many terms crashes field group on save (blank fields)

• I have a custom taxonomy with over 3000 terms
• When creating a new Field Group in MB Builder, I add a Taxonomy field for this custom taxonomy
• When I save, it has a JS error. No fields load. Title does not load, slug does not load, post "id" remains in URL. So I suppose this overwrites all the field data. See console errors below this message.
• I have tried identical tests, with all other plugins disabled, 2019 theme – the problem seems to be choosing this taxonomy with 3000 terms.

ALSO note:

• In a previous MB version I added this taxonomy field to a Field Group, which is displayed on an MB Frontend form -- this works fine still...
• It also works to save this Field Group, containing the field (no changes to field).
• So it seems like an issue with ADDING the field type to a Field Group.
• I also tried adding this custom Taxonomy field to an old/existing Field Group, which also breaks.

Fortunately the old fields still work, so I can continue using my existing Field Group... but I need to be able to make more with this taxonomy in it.

Hopefully this helps and you can track this down and fix it. I will check back here if you have any questions.

Thanks!

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angular.min.js?ver=1.6.9:124 TypeError: Cannot read property 'fields' of null
    at b.$scope.init (builder.js?ver=3.0.1:137)
    at fn (eval at compile (angular.min.js?ver=1.6.9:242), <anonymous>:4:132)
    at b.$eval (angular.min.js?ver=1.6.9:151)
    at Object.pre (angular.min.js?ver=1.6.9:291)
    at angular.min.js?ver=1.6.9:17
    at va (angular.min.js?ver=1.6.9:85)
    at p (angular.min.js?ver=1.6.9:70)
    at f (angular.min.js?ver=1.6.9:62)
    at f (angular.min.js?ver=1.6.9:62)
    at angular.min.js?ver=1.6.9:62 "<div id="nav-menus-frame" ng-controller="BuilderController" ng-init="init()" class="ng-scope">"
(anonymous) @ angular.min.js?ver=1.6.9:124
8angular.min.js?ver=1.6.9:124 TypeError: Cannot read property 'indexOf' of undefined
    at builder.js?ver=3.0.1:206
    at Array.filter (<anonymous>)
    at m.$scope.getPosts (builder.js?ver=3.0.1:205)
    at fn (eval at compile (angular.min.js?ver=1.6.9:242), <anonymous>:4:144)
    at e (angular.min.js?ver=1.6.9:134)
    at e (angular.min.js?ver=1.6.9:134)
    at m.$digest (angular.min.js?ver=1.6.9:148)
    at m.$apply (angular.min.js?ver=1.6.9:151)
    at angular.min.js?ver=1.6.9:22
    at Object.invoke (angular.min.js?ver=1.6.9:44)
(anonymous) @ angular.min.js?ver=1.6.9:124