RDS PostgreSQL: General error: 7 SSL error: invalid key length

Sometimes I catch an error from RDS PostgreSQL.

SQLSTATE[HY000]: General error: 7 SSL error: invalid key length

Usually it works fine, but sometimes the error.

What could it be? Any ideas?

• Engine: PostgreSQL 9.4.1
• Certificate Authority: rds-ca-2015 (Mar 5, 2020)
• Instance Class: db.m3.medium
• Storage Type: General Purpose (SSD)
• IOPS: disabled
• Storage: 100 GB
• Encryption Enabled: No
• DB Instance Status: available
• Multi AZ: No

The SQL being executed was:

SELECT
    d.nspname AS table_schema,
    c.relname AS table_name,
    a.attname AS column_name,
    a.attndims AS array_dimension,
    t.typdelim AS delimiter,
    COALESCE(te.typname, t.typname) AS data_type,
    a.attlen AS character_maximum_length,
    pg_catalog.col_description(c.oid, a.attnum) AS column_comment,
    a.atttypmod AS modifier,
    a.attnotnull = false AS is_nullable,
    CAST(pg_get_expr(ad.adbin, ad.adrelid) AS varchar) AS
column_default,
    coalesce(pg_get_expr(ad.adbin, ad.adrelid) ~ 'nextval',false) AS
is_autoinc,
    array_to_string((select array_agg(enumlabel) from pg_enum where
enumtypid=a.atttypid)::varchar[],',') as enum_values,
    CASE atttypid
         WHEN 21 /*int2*/ THEN 16
         WHEN 23 /*int4*/ THEN 32
         WHEN 20 /*int8*/ THEN 64
         WHEN 1700 /*numeric*/ THEN
              CASE WHEN atttypmod = -1
               THEN null
               ELSE ((atttypmod - 4) >> 16) & 65535
               END
         WHEN 700 /*float4*/ THEN 24 /*FLT_MANT_DIG*/
         WHEN 701 /*float8*/ THEN 53 /*DBL_MANT_DIG*/
         ELSE null
      END   AS numeric_precision,
      CASE
        WHEN atttypid IN (21, 23, 20) THEN 0
        WHEN atttypid IN (1700) THEN
        CASE
            WHEN atttypmod = -1 THEN null
            ELSE (atttypmod - 4) & 65535
        END
           ELSE null
      END AS numeric_scale,
    CAST(

information_schema._pg_char_max_length(information_schema._pg_truetypid(a,
t), information_schema._pg_truetypmod(a, t))
             AS numeric
    ) AS size,
    a.attnum = any (ct.conkey) as is_pkey
FROM
    pg_class c
    LEFT JOIN pg_attribute a ON a.attrelid = c.oid
    LEFT JOIN pg_attrdef ad ON a.attrelid = ad.adrelid AND a.attnum =
ad.adnum
    LEFT JOIN pg_type t ON a.atttypid = t.oid
    LEFT JOIN pg_type te ON t.typelem != 0 AND t.typelem = te.oid
    LEFT JOIN pg_namespace d ON d.oid = c.relnamespace
    LEFT join pg_constraint ct on ct.conrelid=c.oid and
ct.contype='p'
WHERE
    a.attnum > 0 and t.typname != ''
    and c.relname = 'table_name'
    and d.nspname = 'public'
ORDER BY
    a.attnum;