Hello,
First I apologize I post Opencyclemap specific topic to Openstreetmap forum.
I have not found any OpencycleMap map specific forum by Googling or on Opencyclemap site,
so feel free to provide me redirect reference if applies…
I have noticed long time ago strange behaviour of Opencyclemap, ragarding displaying names ,
mainly of cities/towns/villages, or city parts, for zooms approximately 8-12.
When zooming in from zoom about 7- toward 12+,
the many of such names disappear, and reappear later at higher zoom levels.
Disappearing happens often even for names of big towns, while villages stay.
Sometimes one may guess some strange area on map is a town.
At some zoom levels, the most names almost disappear from map,
and like random chosen names of small unknown villages are scattered across the map.
It seems the disappearing has some near random rules patterns,
perhaps renderer bug, like if names collides with some map feature.
Location: The town Třebíč in South-Moravia in Czech Republic, at zooms 9-13
http://www.opencyclemap.org/?zoom=9&lat=49.21786&lon=15.8823&layers=B0000
Some towns scattered arround
http://www.opencyclemap.org/?zoom=10&lat=49.21786&lon=15.8823&layers=B0000
There is no big town at centre of the map at zoom 10, it it ? 
Just some small towns scattered
http://www.opencyclemap.org/?zoom=11&lat=49.21786&lon=15.8823&layers=B0000
There is no big town at centre of the map at zoom 11, it it ? Small towns disappeared, like if being some wilderness.
http://www.opencyclemap.org/?zoom=12&lat=49.21786&lon=15.8823&layers=B0000
Suddenly many villages at zoom 12, but no town yet in centre,
http://www.opencyclemap.org/?zoom=13&lat=49.21786&lon=15.8823&layers=B0000
At zoom 13, the town finally apppears, but by very small latters ( Třebíč ), while town quarters are by much bigger letters )
Location: City of Prague and its North-East neighbourhood at zoom 11
Zoom 11 is especially hostile to names, and specifically to “big” names.
Is this Central Europe, or Northern Canada, where natives established cycloroutes for hunters ?
http://www.opencyclemap.org/?zoom=11&lat=50.26326&lon=15.17231&layers=B0000
This looks like the capital city of Prague, doesnt it ?
http://www.opencyclemap.org/?zoom=11&lat=50.0499&lon=14.4685&layers=B0000