I'll try to paraphrase the issue as I understand it.

Because of how signals are placed in OpenTTD it's not always possible to keep a consistent signal gap where straight tracks connect with diagonal ones. So what signal placer does is making gap half a tile larger when turning from straight to diagonal and half a tile smaller when turning back. And while shortening the gap is usually not an issue, suddenly enlarging the gap is as it stops trains that were happily following others before it.

So a fix, in this case, would be to make the signal placement tool shorten the gap in all cases where it couldn't keep the gap consistent.

BTW. It even enlarges the gap needlessly sometimes:

UPD It seems that another part of this issue is that the straight track piece has a logical length of 192 units while the diagonal one 128 (256 for two halves). And signal placer uses the visual gap instead of the logical one.

In the case of signals every 1, it won't look good. :/
It would be necessary to move the signals that stand on the inside of the field towards its center in order to keep equal distances. This, in turn, might not look great with some NewGRFs adding other signaling.

I would see a solution for maintaining traffic flow other than not the best looking compaction of signals.
A train entering the section at the end of which there is a red light of a block or pre-signal, would immediately start braking, which would be gentler and spread over the entire section. As a result, on the one hand braking would look much more natural, and on the other hand, slowing down instead of suddenly stopping the train would make the traffic smoother.