[EDIT -- *.LESS ] Any change of a field position in a template resets the css stylesheet

Hello,
I use 3.0.14-rc2a.
Each time I drag and drop a field to another position of a template, it immediatly resets the css stylesheet to the original stylesheet of the template, erasing all the changes I've made.
It's a template I had duplicated from the "item-tabbed" one and renamed it.
My css file is opened and it's just changing in front of my eyes and it's impossible to undo it, I lost all my work.
I hadn't used Flexicontent for three years, never had this problem before, is there something new I should know about or is it a big bug ?

Thanks for your answer

Hello

when you upgraded, and then edited your template,
- then your current :
css/item.css
css/category.css

were copied to:
less/item.less
less/category.less

edit *.less files and change your CSS rules in them
- thus you can still make CSS changes exactly as you did before,
just now you need to do them in the *.less

[edit]
v3.0.15, has some a warning message if you try to edit a CSS file directly
and warns it will be overwritten by the compilation of *.less file

Thank you very much for your quick and clear answer.
I didn't see this warning message cause I was modifying my css file directly in a css editor not in Flexicontent administration.
I have to change my old habits...
Thanks for your work.

Hello

you can still use your text editor,
just edit the *.less files with it