Need Help / Advice Cause I'm RPE 4 Confused

Yesterday I did a 40 minute RPE 4 run after a 10 minute fast warm up walk and my average HR was 157 over the course of the run. That's pretty typical.

Today I did a 1 hour ride at RPE 4 and a 30 minute brick run following a 1 minute transition. I'm just starting to do bricks as part of my HIM plan. My average HR for the run today was 152.

What the heck? I figured today's HR would be closer to yesterdays if not a bit higher. I also averaged 17 seconds faster per mile today. WTF?

I guess my question is how do I get my HR to be closer to 152 always....not just after a bike ride?