Can't reid on custom dataset

[tiRomani]

Hi, I have created a dataset that consists of one single image repeated with a person on a field.
The dataset has the same structure used in mot datasets with det/det.txt, img1 and seqinfo.ini .
I have also run all steps required to include a custom dataset.

Finally I have created a script which loads configs, models, tracker and runs MPNTracker.track over the dataset.
It goes like this:

solver = MOTNeuralSolver(hparams = dict(config))
model, cnn_model = solver.load_model()
dataset = solver.test_dataset()

tracker = MPNTracker(dataset=dataset,
                     graph_model=model,
                     use_gt=False,
                     eval_params=config['eval_params'],
                     dataset_params=config['dataset_params'])
tracker.track('custom_dataset', output_path='output/results/results.txt')

Tracking seems to run correctly, but the output doesn't make sense.
There is one new id for the detection on each of the frames. Like it can't reid at all.

Does anybody has the slightest idea of why this could be happening?