When dependent clauses are joined by a coordinate conjunction, there is no comma because there is not an independent subject and verb after the conjunction.
…I was more concerned when I got there and when I saw his condition.
Sometimes the second “when” is omitted — and it is perfectly correct to do so.
…I was more concerned when I got there and I saw him.
Now it appears — falsely — that there is an independent clause after “and.” Should there be a comma? NO.
The word “and” cannot link an independent clause to a dependent clause. “I saw him” is dependent with the “when” understood.
BEWARE of the dependent clause masquerading as an independent clause and trying to fool you!