Defining a query in an alert rule modifies the tags associated

Defining an Alert Rule. In “Step 2: Define query and alert condition” I create a query to retrieve the time series data. It is a simple time series with one float value for each time stamp.
Under “Expressions” I create a Reduce rule to get the mean. On it I see that the tag “name” has been modified with the letter of the query step appended to this tag.

The resulting tags are the same as before, but with the letter A added at the end of the tag “name”:
{env=“PROD”, mtype=“gauge”, name=“XXXXXXmodule.fridge.temp;env=PROD;mtype=gauge;serial=115767;service_appliance_id=XXXXXXXXXXX;service_appliance_name=XXXXXXX;unit=C A”, serial=“115767”, service_appliance_id=“XXXXXXXX”, service_appliance_name=“XXXXXXXXXX”, unit=“C”}

If I create other queries in different blocks and use them in Expression blocks, then the block letter always appears inside the tag (B,C,D…).

I need to get rid of this tag as I am trying to compare the results of two expressions that come from different queries (but not the queries themselves) and the Math operator doesn’t work if the tags are not the same.