Custom Map tiles Overlay hides my routes highlight

Hello everyone, I'am currently working on a Pcl project that, among other things, displays a custom map.

I have used this tutorial to customize my map :

and this one to add custom map tiles.

and finally I used this tutorial to highlight routes on the map :

My map works well, the custom tiles overlay looks nice and I managed to change the look of the pins on the map (yay!)

Now my problem is this : My highlighted routes are not visible on the map.

I know the routes are being displayed because if I zoom in or zoom out of the map, I can actually see the highlighted routes during the short time the custom tile overlay is loading and is not being displayed.

wich makes me guess that my map tiles overlay hides my highlighted routes.

I wanted to know if this was a known issue because I couldnt find anything about this problem online. I can post my code if requested.

Thanks in advance for any bit of advice or ideas