Sewage Outflow line clogs every 3 months

[Riptide31]

I hope someone can help here. I have a commercial office , built in 2008. Plumbing schedule called for 4" diam sewage line out to our lift station. Problem began 3 mos after we first occupied building. Since that time, 3-4 x per year we have to call a plumber to unclog the line. We had a camera put down and there a junction where the clog recurs. Just looks like there's backpitch in the line to me.
The orig installer won't suggest anything other than no paper towels--and to our credit, years ago we installed electric hand dryers in bathrooms with no help. Just mere toilet paper still clogs the pipes. There are 3 kohler toilets with flushmate pressure assist, 1.6l installed. The last plumber who came, said if we could get larger amt of water w each flush that might keep it clear. He said in his opinion, the line should have been 3". He mentioned a company that might be able to install a sleeve inside the pipe as well (but looks like that would create its own lip and problem). I see no flush mates w 3.5gpf capacity.

Anyone have suggestions for a permanent fix? Jack hammering the concrete slab is something I'd like to avoid if possible. Thx

Video of inspection:

 

[Reach4]

There seems to be significant discontinuity at 28...32 ft.

I don't know if that is the problem identified, or if a belly before that is deemed to be the problem.

I am not a plumber, but I think you should plan on digging if you don't want regular roddings. I don't think that using 3 inch to begin with would have helped.

Bidet attachments could reduce TP use. That could increase the mean time between roddings. Maybe your maintenance people could get their own Clog Hog and a gasoline powered pressure washer. However staying with a rodding specialist is probably better for staff. Maybe schedule a rodding/jetting every 2 months. That is going to be a lot easier on your people if it is not event-driven.