coloring areas under the curves using patch

Hello,

Following some comments/guidance to color the area between two curves I finished using the function patch, but when i do it for several graphs, sometimes I have an strange behavior,

for example:

1. I get some areas that should be colored, without color and when I zoom in the figure with the zoom tool the area automatically colors itself.
2. I get at the end of some curves a stange line that comes back and goes outside of the area.

see attached picture for the strange behaivor and the script I am using for it is as follows:

        plot(time(:,i),GCsignals(:,i))
        set(gcf, 'Units', 'Normalized', 'OuterPosition', [0 0 1 1]);
        hold on
        for j=1:length(peakWindowBegining)
            if pos(i,j)~=1
                plot(time(pos(i,j),i),GCsignals(pos(i,j),i),'o')
                a=(GCsignals(endSignal(i,j))-GCsignals(beginingSignal(i,j)))/(time(endSignal(i,j))-time(beginingSignal(i,j)));
                b=GCsignals(beginingSignal(i,j))-a*time(beginingSignal(i,j));
                base{i,j}=a*time(beginingSignal(i,j):endSignal(i,j),i)+ b;
                plot(time(beginingSignal(i,j):endSignal(i,j),i),base{i,j})
                patch([time(beginingSignal(i,j):endSignal(i,j),i) fliplr(time(beginingSignal(i,j):endSignal(i,j),i))], [GCsignals(beginingSignal(i,j):endSignal(i,j),i) fliplr(base{i,j})],'g')
            end
            

I can see that the problem 1. it might be a display issue? and might not be solvable from my side.... but the 2. might be a problem with the fliplr command? or patch itself? i might be doing something wrong.