Ps4 pro still overheating after fan and thermal paste replaced.

I obtained a ps4 pro from a friend that needed some repairs before being operational. I cleaned the heat vents, replaced the thermal paste under the heatsink and installed a new fan on the system. For a couple weeks it worked fine, but then started giving the "system getting to hot" messages before shutting itself down. I did notice that there was some kind of liquid that had gotten on to parts of the motherboard that I had cleaned off with isopropyl alcohol, but now I'm wondering if it could have caused more damage than I originally thought. The friend I received it from was also an indoor smoker, would that play apart in my issue and would a motherboard replacement be the best bet to fix the overheating issue?