Strange Black-Border Mini-Window Appears During Data Loading, Causing MeTrEx to Freeze

[BeatEhrmann]

Description:

When loading data into MeTrEx, a strange black-border mini-window appears, and the application freezes. This issue also occurs during other operations, making the tool unusable during these moments.

Steps to Reproduce:

1. Open MeTrEx.
2. Load data into the application.
3. Observe a strange black-border mini-window appearing.
4. The application freezes, making it unresponsive.

Suggested Fixes:

1. Investigate Window Issue: Determine the source of the strange black-border mini-window. It could be related to an improperly initialized GUI element or a background process.
2. Address Freezing: Review the application's event handling and threading. Ensure that long-running tasks (like data loading) are processed in a separate thread to prevent freezing the main UI.
3. Improve Stability: Ensure that MeTrEx remains responsive during data loading and other operations by improving resource management and preventing UI lockups.

Resolving this issue is crucial to maintain a smooth and stable experience in MeTrEx, especially during critical operations like data loading.