If i use expression with function add() it runs normaly, but if I use expression with Threads:-Add (parallel implementation) it causes error "Error, continuation task already created for the current task" or "Kernel connection has been lost"

Expression:

Array(1 .. N,1 .. 1/2*N-NR-1,(i, m) -> evalf(Add(cosArr2[modp(k*i,N)]/kl[k],k = 1 .. NR+m-1)+Add(cosArr2[modp(k*i,N)]*alpha[k],k = NR+m .. 1/2*N)))

What am I doing wrong? Can I use two Add in one evalf?

I have saved array calculated with Digits:=5000. Now I want to save it with Digits:=2500. I tried this

read "C:\\math\\lambda5000.mpl";

Digits := 2500;

LArr2500 := LArr5000;

save LArr2500, "C:\\math\\lambda2500.mpl"

But this don't work...