Letter clusters: find the cluster whose inner letter gaps break the pattern

This type of question, asked 2 times: 12 Sep 2024 S1, 25 Sep 2024 S2. All 2 questions below, oldest first.

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Question 1
12 Sep 2024 S1
2 $In the following series, only one letter-cluster is incorrect. Select the incorrect letter-cluster. YCG IMQ SVZ CGK MQU$
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Question 2
25 Sep 2024 S2
24 $In the following series, only one letter-cluster is incorrect. Select the incorrect letter-cluster. ZXU SQN LKI ECZ XVS$
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