LMMS hangs on copy/paste multiple tack long sequence

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### System Information

Windows 11 25h2, Intel(R) Core(TM) i7-4800MQ CPU @ 2.70GHz (2.70 GHz)

### LMMS Version(s)

Versie 1.3.0-alpha.1.998+4cb78c4 (win32/x86_64, Qt 5.15.6, GCC 13-posix).

### Most Recent Working Version

_No response_

### Bug Summary

LMMS is unable to copy like 10 tracks of 2 min at once by selecting all and use CTRL right mouse button to paste them at 2 min so make a total of 4 min. It will hang and not responding.

### Expected Behaviour

Be able to duplicate multiple tacks of a long length. Other wise it will take a lot of extra time to make a song.

### Steps To Reproduce

see above.

### Logs

Click to expand

### Screenshots / Minimum Reproducible Project

CTRL-A to select all. Hold CTRL and copy selection with right click mouse and move to to position.

### Please search the issue tracker for existing bug reports before submitting your own.

- [x] I have searched all existing issues and confirmed that this is not a duplicate.

Start by reproducing the hang in LMMS on Windows using CTRL-A, then copying and pasting the selected long sequence with the described right-click and CTRL action. Trace the copy/paste path involved in duplicating multiple tracks; done means a roughly four-minute sequence is created without LMMS becoming unresponsive.

Written by the indexing model from the issue text.