Trying to draw the schematic for a power divider circuit
Seemingly you haven't got a flood of pro quality answers from advanced microwave designers. But here's a guess. It's essentially the same as I wrote as a comment.
Drawn joints between transmission line parts:
I guess the joint assumes some default wave behaviour. It can well be ok if the strip continues by having only a change of width. But three line joints should have some defined geometry. I have no access to high end design software, so this is only a guess.  I also guess you have at least thought the same when you wrote about maybe missing T-parts.
I suggest that you try to reveal possible fundamental error by trying something simpler which you can check by yourself or which is generally well known and presented identically in textbooks.