Not sure I follow but I will do more testing with more way points. I ran one prior that seemed to act the same way but I honestly forget the details. So speculating on my part will just confuse things
Regarding the speed issue with Tower and Solo.
I did get it to work but apparently there is an issue with solo.
I was told this by a developer.
"It should work although it's possible the speed change won't take effect until the next waypoint if this fix isn't in Solo's version of ardupilot (Solo uses a modified version of AC3.3 and maybe it's missing
this fix). Solo should converge with master in a few months (hopefully) so if this is the issue it should be fixed.."
https://github.com/diydrones/ardupilot/commit/d1808c645d041f4d0729a5a14409236aea7a1744