From the picture supplied my observation immediately went to the router mounting clamp. Do you have room to add another clamp about an inch down from the existing one? Or maybe thicken the existing one.
As previously suggested I would slow down my feed rate a bit for your test cuts.
Your machine has quite a few areas that could be beefed up a bit. Amazing what a few well placed gussets can do.
Hey that's what this forum is all about good folks helping each other improve their craft.
Keep pegging at it. You will get there and then its game on.