confirmed

Confirmed, and the reason is usage of hasTooltip class for label (container set to body), but inside BS modal modalTooltip should be used and container set to .modal (to prevent conflict with main page hasTooltip setting).

Similar to this issue, but was inside an existing layout: #9379
(BS known setting for tooltip inside modals)
But content of this modal is not a layout, but a component view loaded as an iframe: administrator/components/com_messages/views/config/tmpl/default.php

Don't know if this view should be a layout instead, or if an easy way to replace hasTooltip by modalTooltip when inside the modal, and using JForm renderField()...

@brianteeman i have opened a PR to fix issue with tooltip: #9991
In the same time, after many testing with @andrepereiradasilva (#9944 (comment)), it appears that many modals loading modal.php file inside iframe has the same possible issue (not always visible) but too, i've found many cases where there's missing a container div (related to one of the other issue you have opened), and some having other code styles issues.
For this reason, i will do a few PRs, to improve those modals, and have a homogeneous display of modal content when loading a components view (modal.php) inside iframe. ;-)