[TMVA] Pymva test (Keras) failing on 632 and main

[dpiparo]

Check duplicate issues.

• Checked for duplicates

Description

The test PyMVA-Keras-Regression fails on 6.32 and master with this error:

Error: [ERROR] Mean squared error is 115.737 (>30.0)

The test needs to be fixed in order to prevent this unstable behaviour.

This is a blocker for the release of 6.32.00.

Reproducer

See nightlies, e.g. https://github.com/root-project/root/actions/runs/8908577851/job/24464458546

ROOT version

master and 6.32

Installation method

from sources

Operating system

Linux

Additional context

No response