What does "slipping out of the extruder" mean? Where is out? There are multiple potential problems. The machine and toolhead used are also important info needed.

Generally, TPU must have a fully constrained path to the hob gear, and everywhere thereafter until it exits the nozzle. It will attempt to escape any gaps after the the hob gear, and to a lesser extent, it may attempt to explore new ways past the hob gear if it is allowed to enter without a tightly constrained path. Some extruders like an E3D Titan have a small insert below the hob gear that have a small PTFE tube to better constrain the path between the hob gear and hotend. This PTFE tube is cut with a wedge shape and should fit as tightly as possible between the hob gear and whatever idler type (bearing/dual gear) it leverages against. If the PTFE tube gets worn out over time or there is any gap or debris in this area, TPU might find a way to escape and cause problems.