do you mean that it breaks at a higher poundage than rated?
I guess I’m luckier than most. I’ve been using Nanofil over two years and my knots hold. Also, I do t tie it direct due to its lack of abrasion resistance. NOTHING I’ve found yet will outcast it and I’ve tried a bunch. I use a double uni to tie my 2 lb Nanofil to a 4 lb leader, 5 loops each. I will also say that it’s a love /hate relationship. If you drag it over a branch it might break there later for seemingly no reason. I have also landed several fish over 3lbs with it. When it’s unaffected it can be tough stuff.
The crystal fireline I use is much tougher and not near as castable. Also hard to find it in long enough spools. The ice guys and jewelry makers buy a lot of 50yd spools so be careful what you order. Sufix nanobraid is also similar and very good and tough. I use both of those in two pound. In my opinion the Nanofil is worth buying a spool and see if you can get along with it. I also use 4 lb Nanofil on a 6’6” medium action rod with a 1500 reel and it casts a 1/16 a very long way and will stand up to stripers in the 18” range.