Is it wrong to use the relative pronoun "who requested ... who came late"?

I am going to make up two pairs of similar sentences below.

(1a) I have had customers who requested a refund when they returned their items damaged.

(1b) I have had customers request a refund when they returned their items damaged.

(2a) Yesterday, I had two students who went to class late.

(2b) Yesterday, I had two students go to class late.

I came up with the a's. My non-native English speaking friends think they are wrong. The b's are their revised sentences. Are my original sentences grammatically wrong? Please help me. Thanks.