MySQL 8.0.23 tmp table keeps filling up

Question

I have not had this issue with older versions of MySQL including up to 8.0.21 which I run in production within AWS RDS. I have a query that gets run only once a year. Here is the relevant code:

create table medicare_fee_history (
        year int unsigned,
        mac int unsigned,
        locality int unsigned,
        hcpcs varchar(10),
        modifier varchar(10),
        index (mac, locality, hcpcs, modifier),
        non_facility decimal(17, 4),
        facility decimal(17, 4)
) engine = myisam;

load data local infile 'PFALL.csv'
into table medicare_fee_history
fields terminated by ',' enclosed by '"'
(year, mac, locality, hcpcs, modifier, non_facility, facility);

create table medicare_fee_first (
        year int unsigned,
        hcpcs varchar(10),
        modifier varchar(10),
        index (hcpcs, modifier),
        facility decimal(17, 4),
        non_facility decimal(17, 4)
) engine = myisam;

insert into medicare_fee_first (year, hcpcs, modifier, facility, non_facility)
(
        select min(year), hcpcs, modifier, avg(facility), avg(non_facility)
        from medicare_fee_history group by hcpcs, modifier
);

During the insert select I get the following error:

ERROR 1114 (HY000): The table '/tmp/#sql4984_9_3' is full

Table medicare_fee_history has 16042724 rows. To reproduce this, the dataset can be found at https://drive.google.com/file/d/1p7Yf7wsCnBXl7UaxeFC1AP0youl-KCdZ/view?usp=sharing

The query generally returns 10823 rows. If you eliminate avg(facility) and avg(non_facility) it seems to work. There is plenty of space in /tmp. 92% of 100G is free. I set tmp_table_size to max. Here are the current server settings:

mysql> show variables like '%tmp%';
+---------------------------------+----------------------+
| Variable_name                   | Value                |
+---------------------------------+----------------------+
| default_tmp_storage_engine      | InnoDB               |
| innodb_tmpdir                   |                      |
| internal_tmp_mem_storage_engine | TempTable            |
| slave_load_tmpdir               | /tmp                 |
| tmp_table_size                  | 18446744073709551615 |
| tmpdir                          | /tmp                 |
+---------------------------------+----------------------+
6 rows in set (0.00 sec)

mysql> show variables like '%temp%';
+-----------------------------+-----------------------+
| Variable_name               | Value                 |
+-----------------------------+-----------------------+
| avoid_temporal_upgrade      | OFF                   |
| innodb_temp_data_file_path  | ibtmp1:12M:autoextend |
| innodb_temp_tablespaces_dir | ./#innodb_temp/       |
| show_old_temporals          | OFF                   |
| temptable_max_mmap          | 1073741824            |
| temptable_max_ram           | 1073741824            |
| temptable_use_mmap          | ON                    |
+-----------------------------+-----------------------+
7 rows in set (0.00 sec)

Any ideas on how to work around this?