@OP, does R21 measure as 9.8 ohms? In a post, you said all passives check out okay, but I just want to verify.

There is one more simple check you can do . See if TOP225YN is shorted. With power off, see if S-D, S-C and C-D are shorted. You can make this measurement in circuit. Any reading less than 100 ohms is suspicious.

TOP225YN is available at mouser.com for $4.03 USD. If you are not in the USA, TOP225YN can be found on ebay and aliexpress.com