• Your Mathematica version

13.0.0 for Linux x86 (64-bit) (December 3, 2021)

• Your FeynCalc version

FeynCalc 9.3.1 (stable version). For help, use the documentation center, check out the wiki or visit the forum.

• Did you try to reinstall FeynCalc (stable version) using the automatic installer to make sure that you have the latest bugfixes?

Yes

• Does your Mathematica initialization file contain statements that might influence the behavior of FeynCalc? Sometimes external packages may modify `init.m` in unusual ways, causing troubles for other codes.

It is empty.

• Please provide a minimal working example that illustrates the problem and works on a fresh kernel. The example should be provided either by writing the code (as `InputForm`!) directly in the issue text or by attaching a Mathematica notebook. Please do not post code samples as screenshots, PDF files etc.: Those essentially require us to retype everything by hand, which is annoying and also time consuming. Please explain the difference between the current behavior and the expected behavior.

SP[p1,p2]=s2;
SP[p1,p3]=s3;
DiracTrick[DiracGamma[Momentum[p2+p3]].DiracGamma[Momentum[p1]].DiracGamma[Momentum[p2+p3]]]

FCClearScalarProducts[];
DiracTrick[DiracGamma[Momentum[p2+p3]].DiracGamma[Momentum[p1]].DiracGamma[Momentum[p2+p3]]]

FCClearCache[FeynCalc`Package`FCFastContract];
DiracTrick[DiracGamma[Momentum[p2+p3]].DiracGamma[Momentum[p1]].DiracGamma[Momentum[p2+p3]]]

After clearing the scalar products (2nd output), I would expect the evaluation should be free of the Pair DownValues s2 or s3.
However, it seems I get the same result as the 1st output, not free of s2 and s3.
Only after manually calling FCClearCache[FeynCalc`Package`FCFastContract], I get the fresh result I expect. (3rd output)

As documented in the definition of FCUseCache[], FCUseCache[] should know that Pair[] DownValues were cleared, but apparently that is not happening, causing DiracTrick[] to give the unexpected result.