That's a known and frustrating limitation to sliding fields unfortunately.
Just tried an experiment to see if I could gin up a work around and was pleasantly suprised to see this idea work:
Make a copy of field 2, make the text color of this copy the same as the fill color. Put it behind Field 1. Do the same with a copy of field 2 and put it behind field 1. Copying the fields copied their sliding properties so they will slide just like the original fields but when a field on top shinks to a smaller height than the field next to it, the fill color of the field behind it--that's the same height as the field next to--makes it look like it has not done so.
Known limitations to this trick:
- The fields placed behind must have exactly the same dimensions and text styles as the originals except for the text color.
- The fields cannot have borders, only fill colors as the borders will put a line under the last row of text on the top fields--ruining the effect of this trick.