Maybe because it is made to sense the infrared spectrum, that it might pick up heat easily whenever it momentarily faces the sun, then requiring a cool down before becoming functional again.
My understanding is that it must NEVER EVER face the sun, even for an instant. The sensitive instruments would be destroyed.
Its orbit around the L2 point combined with the annual revolution around the sun, allow it to examine all parts of the universe, except Earth, since in order to view Earth, it would be facing toward the sun.
Sounds like it’s going through menopause.