It may be that when Toolset blocks (e.g. the Button block) are added to the output of a View and styles are applied to those blocks, the styles may be lost when visiting the page on the front-end (if not immediately, then after a page reload).
This can occur if you Update the page before the WordPress auto-save has a chance to fire.
Until this is fixed, the only workaround is, when editing the output of a View block, to be patient when saving the page, so that the auto-save has chance to fire and cement the changes.
You may also find that the issue only occurs when you have the setting enabled to cache the View, and disabling that will prevent the problem occurring.