In 8.7.2.4.1 Vertical edge filtering process,
chroma edges filtering is described as follows

1. The variable nD is set equal to 1 << ( Max( log2CbSize, 4 ) − 4 ).
2. For xDk set equal to (xC/2)+(k << 3), k=0..nD − 1, the following applies. For yDm set equal to (yC/2)+(m << 2), m=0..nD*2 − 1, the following applies

When log2CbSize is 3, nD is 1 and (xDk, yDm) is (xC/2, yC/2), (xC/2, yC/2+4)
It makes two problems.

1. When (xC / 2) is not multiple of 8, the chroma edge is filtered. but it is not matched with HM8.0
2. (xC/2, yC/2+4) is invalid filtering position because chroma ctb is 4x4

Horizontal chroma filtering has also the same problem.