Noise when starting playing

I am writing a piece for a big orchestra and it has worked fine until now. I am using VSL together with Dorico. The last two days the following happens when I start playing the file. A big bang starts the music. Most instruments works, but not contrabass clarinet, contrabassoon, bass trombone, piano and harp. They throwing out a big noise in the lower register. They have nothing to play in the beginning of the piece, but they play any way. It doesn’t´t matter if I start in the middle of the piece, those instruments starts with a terrible noice any way and then continue play as they should.
Anyone knows what the problem is?
Yours sincerely lgcello

Welcome to the forum, lgcello. So the noise only happens when starting the playback, not in the middle while playing back, right?
What VST instrument(s) are you using? Do you use Noteperformer and if so, what version is it? With some slightly older Noteperformer version there is a known issue where suddenly loud digital noise might occur, but it is fixed in the meantime.
On the other hand, that noise with Noteperformer would happen anytime during playback and mostly not during start. Is that what you describe really noise, or is it just some really low or high tones?
Another thought, what audio driver are you using and what is the driver’s block size set? Increasing the block size might also help.

Hello! I solved the problem. I took an old security file which worked and I wrote the missing music again and then it worked. I have no idea why the file was corrupt. But now it works again. Thanks very much for your help.
Another question: I am writing a long piece and the computer are going slower and slower. Is it better do it in two parts? And in that case two different files or two flows?
Yours sincerely lgcello

Can you tell us a bit more about your piece, and about your computer configuration? How many instruments are in your orchestra? How many bars in your flow? What kind of CPU does your computer have, what speed is it, and how much RAM does it have? I guess it will be a fast and powerful computer if you are using VSL, but specifics will help.

Are you using condensing? If so, switch it off while you are doing input and editing.

The piece I write will take a whole evening concert to perform (around 90 minutes) I have written ca 45 minutes so far. The orchestra is of Mahler´s size. 5 each of the winds, quite a lot of percussions, piano, harp and strings ( sometimes divided in several parts). There are around 1300 bars so far. (half the piece) It has worked very well so far, but now the computer are getting very tired. I am using a MacBook Air with 16 RAM and 1 TB SSD.
If I understand it right, so will Flow 2 also work with Flow 1 to recalculate, then it will also slow down the computer. If I use two different files, perhaps it will work better. I am also consider if I should buy a new computer with more power. I am using Dorico 2.2.20, but I will upgrade to Dorico 3.

lgcello, other users have found the number of CPU cores to be important for performance. Are you running 2 cores, or 4? For a project that size, you really need 4 (at least).

1,8 GHz Dual-Core Intel Core i5