@CobraA (CobraA) Thanks for testing with various versions of Blender, that makes it much easier to pinpoint the issue.

Testing the file in 2.80, it shows different motion path problems, so my guess is that the reported behaviour was introduced in a change that actually fixed other issues.

I did some digging, and it seems that this is caused by rB4db2a08281f8495421938e0b2f6a802420afba36. That changed the parameter current_frame_only=true to range=xxxxx_CURRENT_FRAME for bones but range=xxxxx_CHANGED for objects. As animviz_calc_motionpaths() only updates the motion path for the current frame if range=xxxxx_CURRENT_FRAME, this introduced the observed difference between the handling of bones and objects.

This issue can be fixed by this change:

diff --git a/source/blender/editors/transform/transform_generics.c b/source/blender/editors/transform/transform_generics.c
index bb4d50fcf54..716df24f195 100644
--- a/source/blender/editors/transform/transform_generics.c
+++ b/source/blender/editors/transform/transform_generics.c
@@ -1102,7 +1102,7 @@ static void recalcData_objects(TransInfo *t)
 
     if (motionpath_update) {
       /* Update motion paths once for all transformed objects. */
-      ED_objects_recalculate_paths(t->context, t->scene, OBJECT_PATH_CALC_RANGE_CHANGED);
+      ED_objects_recalculate_paths(t->context, t->scene, OBJECT_PATH_CALC_RANGE_CURRENT_FRAME);
     }
 
     if (t->options & CTX_OBMODE_XFORM_SKIP_CHILDREN) {

I'll discuss with @Sergey Sharybin (sergey) to see if this is the appropriate fix.

@Sybren A. Stüvel (sybren), good find! Just commit it ;)

@Sybren A. Stüvel (sybren) My pleasure, Thank you for taking the time to take a look at it.