.I am wondering what "glue " to use to repair the damage without damaging the sideframe
It is possible that the side frames are moulded in Acetal or otherwise known as Delrin for impact resistance. If it is a new purchase, then my advice would be to take it back and ask for an exchange, repair or refund.Acetal plastics are very hard to bond. CA often just fractures off, but I have had good results with this http://www.selleys.com.au/adhesives/household-adhesive/quick-fix-adhesive/plastics-glue/ on both acetal and nylons (which are also a bugger to glue).
If it is not new and under warranty, then you are best to make some tests on the plastic first. Buy any of the plastic glues from a model shop, and place a small drop on the back of the side frame where it will not be seen. Wait about 5 minutes, then poke at it and smear it off.
If it has not 'eaten' into the plastic of the side frame, then most likely the frame is made of Delrin, in which case it is very difficult to glue, and there are almost no readily available glues that will bond it.
If it does 'eat' into the plastic, then use the plastic glue you bought to glue it back together.