Html notes - slow UI and problem with colors


I use Joplin 1.3.15 on Windows 10.
I have imported my notes from Evernote both in Markdown and HTML. Some notes I need to conserve in HTML.
I have realized everything works well with Markdown notes but as soon as I start opening HTML notes, UI gets slow and laggy (it can freeze several seconds when opening a note).
Also, when switching between Markdown and HTML notes, the colors often get messed up in different ways, usually the styling of the rendered Markdown note will change to match the previously opened HTML note.

I am wondering if those are known issues, to be expected with HTML notes?