To avoid such condition

1) Check if the model is placed correctly in the software, place the model such a way that maximum surface much touch the heat bed.

2) This happens if the Kapton tape loses stickiness or the model bottom is too small. In such cases, you can use hot melting glue gun to glue the parts. You can also add support structures to support the model.

3) Use double sided kapton tape which has adhesiveness on both the sides of the tape hence would help to hold the 3D printed model.