Well, the only way to unbreak High Rise Hijinks was to make the intended talisman solution the full intended solution - I found another solution that completes the level under the talisman rules, but it uses all the tools so is acceptable enough.
Note that I haven't reduced the time limit to 3 minutes, but I increased the save requirement from 48 to 49, which might be a bit confusing, but the talisman wasn't called "Technical details" for nothing.
Another option is to keep it at 48/50 and allow all the recent backroutes, but have the talisman be to save 49/50.