screen would be unresponsive, reboot, or digitally split, randomly

Phone would be perfectly usable for hours, then the screen would become unresponsive, or the apps will take a long time to load. Sometimes it will get digitally distorted, or show u an app u had previously opened.

Backstory:

Phone was never dropped in water, never been out of the case for more than 5 mins, been drop from waist level but no physical damage or screen damage ever.

iPhone SE was fine, had Apple store replace the battery back in Dec 2018 to make performance better. May 2019, all of a sudden, phone will not hold a charge anymore, and would randomly reboot. Apple Tech insisted a battery replacement would not fix the problem but I proceeded anyway. Upon examining they found out that a missing part was not placed back in called the Battery Cowling that kept the battery in place. They replace said battery and the phone was back to normal again for about a month before this new problem started.

Apple tech is absolutely clueless what could be wrong and have even offer to take it in as a trade for $56… (he did a restore, opened up the device, reconnected all connection to make sure nothing is lose)

Difference from before, battery still charges and phone holds a charge.

Steps Moving Forward:

Steps I have thought about doing is selling the phone, with or without disclosing the problem… I probably will disclose it, just because I have integrity. However, I would like to get at least $150 out of this phone… I thought of replacing the screen, but I don’t know if it’s worth it…

help!!!