Redshift Maximum tables limit exceeded problem, how to prevent this behavior

Hi, we have recently deployed our data warehouse into Production. There is lot of ETL done using stored procedures within Redshift.

my ETL workflow is as follows,

Data from DB2 system is staged within Redshift. and then the data is moved into Data warehouse using Redshift procedures. I have a 2 node RA3 cluster. (with node Type: ra3.xlplus)

every now & then my ETL is failing with following error

SQL Error [XX000]: ERROR: Failed to incorporate external table "xxxxxx.covera" into local catalog. Maximum tables limit exceeded. The maximum number of tables per cluster is 20000 for this instance type. The limit includes permanent and temporary tables.

In my ETL redshift procedures, I use cross database queries in the procedures.
I cannot disable Temporary Tables as we are using CTE, and local temp tables to perform ETL using Redshift procedures.

when I queried STV_TBL_PERM, I see there are lot of Temporary Tables created within Redshift, I have seen ~20000 tables. I can understand why I am getting above error.

I am not able to understand the need for this temporary tables by redshift, and why are they persisted forever.

Table name looks exactly like this localhost@232987@465587@ .

how can I delete these temporary tables automatically?

Can you please give some insight.

Regards Shiv