trouble extending blanks in x-sheet layers

[2dbert]

Hello,
I'm fairly new to working with TvPaint, I enjoy it very much so far (it's a lovely program, dear developers! Thank you!), but here's a problem I ran into:
I use the X-sheet to match my timing of a number of layers to sound, and so it happens fairly often that I want to extend a stretch of blanks in single layer columns. When I do this by clicking on the bottom blank and stretch it's length, shortly after that the extension isn''t blanks anymore but has been replaced with the last image frame that sits just before the stretch of blanks. If I change it back to blanks, it will jump back to the previous image a few moments later.
I know I could turn the x-sheet layer into an animation layer once I'm happy with the timing, and get rid of the excess images then, but is there a direct way to fix this? I'd like to do cleanup and colour layers to assign those as source layers to the same x-sheet, and it would therefore be handy to have the x-sheet as it is supposed to be, otherwise the workaround will have to be applied to each of those layers.

Any idea what I do wrong, or has this been discussed in a previous thread I couldn't find?

Thanks!

[2dbert]

Ok, in case this is useful to know for anybody except me, here's what I worked out in the meantime:
The odd behavior described above applies seemingly only to stretches of blanks created by dropping source images into an X-sheet column but leaving gaps in between the images. If the duration of those gaps is manipulated after, it can happen that it plays up as described.
However, if a figure that is not linked to any source image is being typed into the field that is supposed to be a blank, all works fine. That's the way the manual suggests to operate, so I guess I should have tried before posting my question, ahem.
Also, adding an empty instance into the source layer where the blank should be can have it's timing changed in an X-sheet column without any problems. So, all is well.