Layered decoding is known to provide efficient and highthroughput implementation of LDPC decoders. However, the implementation of layered architecture is not always straightforward because of memory update conflicts in the a posteriori information memory. In this paper, we focus our attention on a particular type of conflict that is due to multiple-diagonal sub-matrices in the DVB-S2, -T2 and -C2 parity-check matrices. We propose an original solution that combines repetition of the concerned layers and the write disable of the a posteriori information memory. The implementation of this solution on an FPGA-based LDPC decoder led to an average air throughput of 200 Mbit/s with a parallelism of 45 and a clock frequency of 300 MHz. Increasing the parallelism to 120 led to an average air throughput of 720 Mbit/s with a clock frequency of 400 MHz on CMOS technology.