ImageryProvider loads tiles slower and slower...

Hi,

I'm using the TileMapServiceImageryProvider to load custom tiles in my app and I noticed something: the loading time is getting slower...

I tried my app with different Cesium versions (from 1.14 to 1.18):

1.14 : 20 sec
1.15 : 32 sec
1.16 : 30 sec
1.17 : 75 sec
1.18 : 200 sec

It seems that since the 1.17 the loader gets "stuck" on the 2nd tile level.

Do you have the same problem ?