Even if you are just downloading static data using the TIA (Toolkit for integration and analysis) Python package, it can interfere with the Bloomberg Excel add-in.
When connecting to Bloomberg using TIA, it starts listening for Bloomberg events. Even after you've finished using it, it may still be listening to and responding to those events. This means that if you're using the Bloomberg Excel add-in to get real time data, that can start taking longer as the TIA package is also processing those events and slowing down your Excel session. This can happen even if you have no active TIA objects and are not using it to stream live data.
Instead of using TIA, we recommend that you use Bloomberg's own Python API, blpapi (https://www.bloomberg.com/professional/support/api-library/).
If you get an error about mismatching Bloomberg API versions when using the blpapi package and the Bloomberg Excel add-in, please see Mismatch between C++ and Python SDK libraries when using blpapi.