Review the item:
While Patrick is sightseeing, Squeeze will either
find a patch of sunlight beneath a window
or he will curl
up under a table lamp.
When you use either ... or, you must have two equal grammatical items. After either, notice that you have half a verb phrase, find. (Will find is the whole verb phrase.) But after or, you have a main clause, he will curl up under a table lamp. The structure is not parallel.
To fix the item, you can change he will curl to curl.