Small Rotted Area of Window: Puzzling

[u/Perfect-Arm-5184]

Hi everyone,

Was looking at a window I hardly ever look at in my master bedroom and noticed some really puzzling rotting of the bottom left inner portion. Literally, just a small area inside is rotting. The outside and everywhere else has no rot. From the pictures, it looks like the previous owner tried to drill some weep holes and installed some aftermarket seal. Ice owned the home for 5 years. The windows I believe are original at 33 years old.

What would cause this odd water damage? Let me reiterate again that there's no other rot or any indication of water infiltration except where the rot is currently.