From your post i would say that it's the overly large edge angle, although the type of plastic the cutting boards are made from could also play a role.
In contrast to what most people think a narrower edge angle lasts longer (within reason)
What i've found is that many generic stainless steel kitchen knives can handle a sharpening angle of ~25 degrees inclusive (when used with care for some time on a reasonable quality cutting board), which if then deburred on the Tormek leather wheel their apex will come out at ~30 degrees inclusive due to the "give" in the leather wheel, which will micro-convex (and thus strengthen) it just enough.
If however i find that my customer is an ignoramus/brute/Shrek/idiot then i increase my sharpening angle to ~30 inclusive,of which the apex will measure ~35 degrees inclusive after deburring.
My own rule of thumb: (the edge should be) as thin as possible, but thick enough.
The knife wielder can then use a good quality (mirror-) steel on that edge, and later maybe a good ceramic rod to prolong the knife's useful sharpness before you get a new request to perform your magic on the knives again.
The happiest customers are those that need your services the least, but most likely they will be your returning customers
In contrast to what most people think a narrower edge angle lasts longer (within reason)
What i've found is that many generic stainless steel kitchen knives can handle a sharpening angle of ~25 degrees inclusive (when used with care for some time on a reasonable quality cutting board), which if then deburred on the Tormek leather wheel their apex will come out at ~30 degrees inclusive due to the "give" in the leather wheel, which will micro-convex (and thus strengthen) it just enough.
If however i find that my customer is an ignoramus/brute/Shrek/idiot then i increase my sharpening angle to ~30 inclusive,of which the apex will measure ~35 degrees inclusive after deburring.
My own rule of thumb: (the edge should be) as thin as possible, but thick enough.
The knife wielder can then use a good quality (mirror-) steel on that edge, and later maybe a good ceramic rod to prolong the knife's useful sharpness before you get a new request to perform your magic on the knives again.
The happiest customers are those that need your services the least, but most likely they will be your returning customers