In vanilla there is a small problem that has lasted for a long time, and it is not sure whether everyone has this problem. When opening the fifth action bar, the fifth action bar will be a little longer than the first and second. Can you fix this problem?

You enabled "Bars editor" option in 2nd page in GUI?

Yes. I edited the third action bar.

Try change this line https://github.com/EsreverWoW/ShestakUI_Classic/blob/master/ShestakUI/Modules/ActionBars/Bar5.lua#L63
to
b:SetPoint("LEFT", b2, "RIGHT", T.Scale(C.actionbar.button_space), 0)

OK. The problem was fixed with this method. thanks.