It took me a while to pin this down, but I have finally done so. Sorry for the delay.
The reason you’re getting no whole bar rest in the first bar is that you have overridden the voice of the triangle note in the second bar to use one of the “extra” voices via Edit > Percussion. Those “extra” voices are never padded with rests, which explains why there is no rest before that note, which happens to be the first note in the combined five-line presentation of that percussion kit. From looking at your kit, though, you shouldn’t need to use these extra voices anyway: you can select each instrument in your percussion kit and assign a stem direction there. You should try that, and then use Edit > Percussion > Reset Destination Voice to put things back to their default voice assignments. In general it’s better to make those choices in the kit and then only override them in specific cases, rather than to do everything by overriding the voices in the music on a case by case basis.
This is also the cause of the problem with the tuplet in the following bar, though you should find that provided you select the tuplet bracket/number as well as the notes, you can successfully change them into an extra voice if need be.