Altsearch crashing on LO 6.4


I need to convert a large number of documents from Libreoffice to plain text/markdown, and I can’t find anything working for me. If I use libreoffice with the CLI, multiple spaces & tabs are preserved, but by removes bold and italics. Pandoc preserves bold and italics, but squashes spaces and tabs. i asked a question a while back and the nice suggestion I got was to substitutes two or more spaces / tabs with special characters, use pandoc to convert, then replace again. That sounds like a nice idea, but now I’m no longer able to do batch search and replace of documents. I’m trying to use AltSearch, but this has only been tested for Libreoffice 5, and my computer crashed three times already when I tried to do that.

Does anyone know how to make batch substitutions many documents with LO 6?
Or, alternatively, does anyone know where I can download LO 5? I would use it for this task, then upgrade back.
Or maybe a tool to process odt documents in Python for instance? Or writing a macro?

All I need is replacing two spaces with, say, ¬, and tabs with ¤, then I can use Pandoc to convert all my odt to txt, then I can use sed or vim to replace those signs back.

Specs: Ubuntu 18.04, LO, AltSearch 1.4.2.

Thanks in advance for your help!

Have you tested with a clean profile and reinstall Alt-search, Menu/Help/Restart in Safe Mode