为什么测试集的loss几乎不变？

[JaylanMei]

我直接按照readme进行训练，发现evaluate的loss几乎一直不变，几乎一直保持下面的大小
loss: OrderedDict([('loss_ce', 0.187), ('loss_counter', 0.114), ('loss_bbox', 0.151), ('loss_giou', 0.299), ('loss_self_iou', 0.138), ('cardinality_error', 3.56), ('loss_ce_0', 0.173), ('loss_counter_0', 0.115), ('loss_bbox_0', 0.343), ('loss_giou_0', 0.511), ('loss_self_iou_0', 0.242), ('cardinality_error_0', 3.56), ('total_loss', 4.075)])
请问这是怎么回事？