calibre viewer shows "Unhandled error: Uncaught InvalidStateError: Failed to execute 'surroundContents' on 'Range'" after RegExp searching in epub-file

[Sergey M.]

Environment:
xUbuntu 18.04.5
Python 3.6.9
calibre 5.7.2; was installed over the 3.21.0 version (from of.ubuntu-repository) using command
 sudo -v && wget -nv -O- https://download.calibre-ebook.com/linux-installer.sh | sudo sh /dev/stdin

STR:
1. open the book from attachment in Calibre E-book viewer
2. open the Search dialog (Ctrl+F), select Regex type of searching
3. enter to the Serch field value \s+\w+ *: *\w+ *= *\w+
4. press Find next match trice (starting from the beginning of the book)
5. make sure the error is present

(full text of the error message):
calibre, version 5.7.2
ERROR: Unhandled error: Uncaught InvalidStateError: Failed to execute 'surroundContents' on 'Range': The Range has partially selected a non-Text node.<br><span style="font-size:smaller">Error at userscript:viewer.js:17926:15</span>
Traceback (most recent call last):
    at Number.onload (userscript:viewer.js:16991:21)
    at IframeBoss.content_loaded (userscript:viewer.js:25274:18)
    at IframeBoss.content_loaded_stage2 (userscript:viewer.js:25302:26)
    at IframeBoss.show_search_result (userscript:viewer.js:25836:22)
    at IframeBoss.ensure_selection_visible (userscript:viewer.js:19428:17)
    at wrap_range (userscript:viewer.js:17926:15)
Error: Failed to execute 'surroundContents' on 'Range': The Range has partially selected a non-Text node.

(should you need additional information please ask me in comments or any other ways)

[Kovid Goyal (kovid)]

That regex gives me no matches. Since the problem is with the third
match why dont you just post it as plain text.

 status incomplete

[Sergey M. (msvcontact)]

problem is not in RegExp as I got, but in the epub book rendering (which is executed after opening that particular search result).
so I attached here the screenshot with overall situation - RegExp + list of results of search + result number (4th) + the error message and reader's page view (was emptied after error).
Should You need any other information, let me know here in comments.

[Sergey M. (msvcontact)]

(add.)
bug repeated in almost the same way with another epub file (1st attachment - descriptive screenshot to the whole issue)

[Sergey M. (msvcontact)]

(2nd attachment - epub file)

[Kovid Goyal (kovid)]

I cannot replicate, with either of your attached files. See screenshot.

1) Uninstall the distro calibre, dont install over it.
2) Try to reproduce with a clean calibre config CALIBRE_CONFIG_DIRECTORY=/tmp/test ebook-viewer file.epub

[Kovid Goyal (kovid)]

Actually, never mind, am guessing you are in flow mode not paged mode.

[Kovid Goyal (kovid)]

Fixed in branch master. The fix will be in the next release. calibre is usually released every alternate Friday.

 status fixreleased