Question: DESeq2:Why is there an oblique line in my MA picture, which happened before, what caused this?
Those lines are from genes with very low counts of genes, e.g. 2 counts in the treated group, 1 count in the control group. If you want to remove them you can perform some minimal filtering, e.g.:
keep <- rowSums(counts(dds) >= 10) >= x dds <- dds[keep,]
Where you choose
x to be a small number of samples.