90 degree bends in shower waste

[snowhead]

In answer to the O.P question,
Yes it will cause problems, it will block faster than normal and be near impossible to clear easilly.

Is that a rather large notch cut out of an already notched joist?

 

[Allgoode]

Redo if poss as you are storing up trouble in the not too distant future.
Glued swept bends are best & as few as possible.
As previously mentioned the setup shown is pants & can guarantee there will be issues.
Can you re-orientate the shower tray, may be a longer run but with far superior flow &/or raise the tray to get good fall to the drain, only needs an inch or two max.
Cheers,
Andy

 

[moonlight]

Cut the black waste back, rotate the shower outlet and connect straight on with a coupler and a short length of waste.

 

[gpbeck]

In answer to the O.P question,
Yes it will cause problems, it will block faster than normal and be near impossible to clear easilly.

Is that a rather large notch cut out of an already notched joist?

And reinforced with MDF?

 

[king of pipes]

You should be able to do it like this