Tag autocomplete not working after "&" or formatted text

This is a bug in the new layout when running under the current version of Firefox (61.0.2). Disabled all plugins and still seeing this problem.

Steps to replicate...

- Create a new line with a tag.

. Test tag #alpha

- Create a second line with an ampersand filled by some text and #a – the autocomplete popup does not appear as expected

. Another line & test #a

- Delete the ampersand and the #tag popup works as expected

. Another line test #al

- Highlight the word "line" and make it italic (CTRL+i) - autocomplete popup stops working again

. Another line test #alp

- If you move the cursor before any formatted text or ampersands, #tag popups work as expected

. Another #a line test

Really want autocomplete to work all the time. Thanks.