How to add back borderline of my figure.

Here is my code. When I add last sentence alpha(0.5), the borderline of my figure disappear somehow? I mean the upper and left borderline disappear, how do I add it back? Many thanks

figure(1);
x = -4:8;
y = x.^3;
upper = x.^3-30;
lower = x.^3+30;
plot(x,upper,x,y,x,lower);
hold on;

fill([x fliplr(x)],[y fliplr(upper)],[1 0 0]);
fill([x fliplr(x)],[y fliplr(lower)],[1 0.75 0]);
% alpha(gcf,0.5);
x1 = 1:2;
Ylim = get(gca,'YLim');
y1 = ones(1,length(x1)).*Ylim(1);
y2 = ones(1,length(x1)).*Ylim(2);
fill([x1 fliplr(x1)],[y1 fliplr(y2)],[1 0 0]);
alpha(0.5);

Answer 1

[Walter Roberson]

This is a long-standing bug; there is a work-around but no cure for it.

I do not remember the detail of the bug, and I am having trouble locating the appropriate posting, but I remember that Jan knows the details.

[HKmathfin]

Where is the workaround? Or can you forward this to Jan? Thanks a lot.

[Walter Roberson]

The work-around involved making the axes just a tiny bit bigger, I think.