Thank you for the additional details and attempting to reproduce on your device. I checked again, and my experience is: After saving the Behavior setting (as Heel Down or Toe Down) for one block on a preset, upon leaving the preset and returning, the Behavior setting reverts to Toggle.
For additional troubleshooting, I exported a few presets and opened the corresponding .hlx files in a text editor. The particular values of the corresponding '@behavior' param for a given block may help reveal the bug to Line 6:
After saving as Toggle and exporting the .hlx, '@behavior' is 0
After saving as Heel Down and exporting the .hlx, '@behavior' is 1
After saving as Toe Down and exporting the .hlx, '@behavior' is 2
After leaving the preset, returning, and exporting the .hlx, '@behavior' is occasionally true
This occurred several times (but not every time) upon re-exporting a previously saved preset. Regardless of whether '@behavior' reverted to 0 or was true, in HX Edit and directly on my Helix, the corresponding EXP Behavior setting is Toggle.