I have similar issue as here: Preventing clipped labels from QGIS Server WMS in Leaflet JS
But I have issue with cutting of symbols on border of tiles not with labels.
Here is a picture with my situation:

Red line is boundary of two tiles and as you can see pictures with navigation signs are cut off. I tried all what I found on whole Internet but without success.
How do I change setup of UMN MapServer to gave me good result?