Description:
in libre office calc if I add a mathematical formula using the insert | object | formula option and then save the file selecting the xlsx format the formula is missing when the file is re-opened

Steps to Reproduce:
1.open calc application and create new file
2.select a cell
3.from the menu select insert then object then formula
4.add a formula (just choose one from the examples)
5.save the file as xlsx format
6.close calc application
7.re-open the file
8.the formula is gone

Actual Results:
blank cell where formula should be

Expected Results:
formula to be retained


Reproducible: Always


User Profile Reset: No

Additional Info:
tried with both xlsx and xlsx open xml format

Version: 7.1.8.1
Build ID: 10(Build:1)
CPU threads: 8; OS: Linux 5.14; UI render: default; VCL: gtk3
Locale: en-GB (en_GB.UTF-8); UI: en-US
Calc: threaded