Are you using a good quality pair of wrenches?
The community has the following notes on Carbide Compact Router/Makita RT0700/0700 shaft and collet/nut wrench sizes:
- 13mm — note that this must be low profile.
- Amazon.com
- Bicycle cone wrenches work as well such as the 13mm Park Tool PT-09 Shop Cone Wrench
- Asahi low profile 11/13mm wrench
- McMaster-Carr Tight-Clearance Open-End Wrench with Black Finish, 13 mm Size, 4" Overall Length (sourced from Martin as of mid-2020)
- 22mm — a stubby wrench is well-suited for this, and handier due to the low torque requirements
c.f.,