Hi Catherine,
If your shuttle is diving that much you need to increase your warp tension. AND, check to see that your warp is going over the thread beam at the back and not coming into the heddles directly from the warp beam. This is not normal for a Jane loom unless you tension is too loose :) Hope this helps.

My table loom is a beautiful 8 shaft original Woolhouse Tools Carolyn loom with 2 back beams. I have loved everything about this loom since I bought it new 20 years ago...EXCEPT for the lack of a shuttle race. I was actually prepared to sell it this year, until I had the bright idea to add my own shuttle race. It has a bottom swinging beater, so was very easy to do. I expect I'll now be using this loom until I die. Not everyone is bothered by the absence of a shuttle race, but, like you, I really needed to add one to have an enjoyable weaving experience.

Hi, what is a “cable canal 30cm”? and what is alien tape? Thanks.

I thought I replied to this post but I do t find it now. Anyway, the nano tape aka alien tape, does it stick ok to the beater bar wood? Is you cable canal made of plastic and light weight? Is the canal 3 cm wide?

Yes, the tape sticks really well and is removable without problems when not in use. You don't have to use it over the whole lenght, I just took three pieces of around 2 cm.
The cable canal is as you describe.