Combo bug in street fighter 5?

is there a combo bug because i just tried two standing mp’s with m bison and it connected but the combo bar aka indicator did not registered it as 2 hits.

and then i tried one standing mp into cr lp the standing mp hit but the cr lp did not hit even though in terms of frame data
st mp is + 6 on hit and cr lp is 4 in terms of start up frames it should work in terms of frame data but it did not work.

so im asking is there a combo bug if not can somebody explain what this means.