I doubt that's the only reason but according to this table [0], AGC triplets are 2x more prevalent than UGC in that bacteria.
Edit: this the frequency of that codon being used o the genome sequence. But the assumption could be that it is also preferably produced as a t-RNA so it can replicate its genome efficiently.
It's more likely that they have introduced errors, or non-preferred patterns, which affect the number of replication forks and stall the replication machinery.
