I was having this problem with a 20w16a --> 20w17a world. Appears that if I break the dirt blocks underneath the saplings (I've been breaking a 4x4 swath, just in case...), and then replacing the hole with the same dirt backs, the same saplings will grow. Seems to reset some property on the saplings and/or the dirt that's changed in the latest snapshot...
I don't think I have a way to upload the world to any filesharing sites or anything from Xbox one with the stuff I have. Could also be laziness but yeah...
I was having this problem with a 20w16a --> 20w17a world. Appears that if I break the dirt blocks underneath the saplings (I've been breaking a 4x4 swath, just in case...), and then replacing the hole with the same dirt backs, the same saplings will grow. Seems to reset some property on the saplings and/or the dirt that's changed in the latest snapshot...