具有LSTM的用于Keras中的句子相似性的Siamese Network定期给出相同的结果

I'm a newbie in Keras and I'm trying to solve the task of sentence similairty using NN in Keras. I use word2vec as word embedding, and then a Siamese Network to prediction how similar two sentences are. The base network for the Siamese Network is a LSTM, and to merge the two base network I use a Lambda layer with cosine similairty metric. As dataset I'm using SICK dataset, that gives a score to each pair of sentences, from 1(different) to 5(very similar).I'm a newbie in Keras and I'm trying to solve t