Slow performance of historic task instance query

Aggregate  (cost=71618007.93..71618007.94 rows=1 width=8) (actual time=412438.951..412438.951 rows=1 loops=1)
   ->  Unique  (cost=71617921.29..71617946.04 rows=4951 width=37) (actual time=412438.480..412438.837 rows=517 loops=1)
         ->  Sort  (cost=71617921.29..71617933.67 rows=4951 width=37) (actual time=412438.479..412438.585 rows=517 loops=1)
               Sort Key: res.id_
               Sort Method: quicksort  Memory: 65kB
               ->  Nested Loop Left Join  (cost=1000.29..71617617.46 rows=4951 width=37) (actual time=8724.729..412436.174 rows=517 loops=1)
                     Join Filter: (((a.resource_id_)::text = (res.proc_def_key_)::text) OR ((a.resource_id_)::text = '*'::text))
                     Filter: (((res.execution_id_ IS NOT NULL) AND (a.resource_id_ IS NOT NULL)) OR (res.execution_id_ IS NULL))
                     ->  Gather  (cost=1000.29..71617125.39 rows=4951 width=85) (actual time=8724.708..412428.707 rows=517 loops=1)
                           Workers Planned: 1
                           Workers Launched: 1
                           ->  Parallel Index Scan using act_idx_hi_task_inst_end on act_hi_taskinst res  (cost=0.29..71615630.29 rows=2912 width=85) (actual time=5326.334..406883.498 rows=258 loops=2)
                                 Index Cond: (end_time_ IS NULL)
                                 Filter: ((assignee_ IS NULL) AND (NOT (SubPlan 1)))
                                 Rows Removed by Filter: 5500
                                 SubPlan 1
                                   ->  Materialize  (cost=0.00..21180.98 rows=164236 width=37) (actual time=0.008..50.873 rows=52452 loops=10492)
                                         ->  Seq Scan on act_hi_identitylink hil  (cost=0.00..19075.80 rows=164236 width=37) (actual time=0.011..64.155 rows=57519 loops=2981)
                                               Filter: ((group_id_ IS NOT NULL) AND ((type_)::text = 'candidate'::text))
                                               Rows Removed by Filter: 3416
                     ->  Materialize  (cost=0.00..405.43 rows=1 width=36) (actual time=0.001..0.003 rows=1 loops=517)
                           ->  Seq Scan on act_ru_authorization a  (cost=0.00..405.43 rows=1 width=36) (actual time=0.012..1.235 rows=1 loops=1)
                                 Filter: ((type_ < 2) AND (resource_type_ = 6) AND (((user_id_)::text = ANY ('{demo,*}'::text[])) OR ((group_id_)::text = 'camunda-admin'::text)) AND ((perms_ & 4096) = 4096))
                                 Rows Removed by Filter: 7860
 Planning time: 0.692 ms
 Execution time: 412440.513 ms

	Aggregate  (cost=13050.46..13050.47 rows=1 width=8) (actual time=832.411..832.411 rows=1 loops=1)
	   ->  HashAggregate  (cost=12916.14..12975.84 rows=5970 width=37) (actual time=832.101..832.293 rows=517 loops=1)
			 Group Key: res.id_
			 ->  Nested Loop Left Join  (cost=1000.71..12901.21 rows=5970 width=37) (actual time=50.539..831.489 rows=517 loops=1)
				   Join Filter: (((a.resource_id_)::text = (res.proc_def_key_)::text) OR ((a.resource_id_)::text = '*'::text))
				   Filter: (((res.execution_id_ IS NOT NULL) AND (a.resource_id_ IS NOT NULL)) OR (res.execution_id_ IS NULL))
				   ->  Gather  (cost=1000.71..12391.31 rows=5970 width=85) (actual time=50.509..829.315 rows=517 loops=1)
						 Workers Planned: 1
						 Workers Launched: 1
						 ->  Nested Loop Anti Join  (cost=0.71..10794.31 rows=3512 width=85) (actual time=28.345..823.089 rows=258 loops=2)
							   ->  Parallel Index Scan using act_idx_hi_task_inst_end on act_hi_taskinst res  (cost=0.29..1456.38 rows=5825 width=85) (actual time=0.011..5.919 rows=5244 loops=2)
									 Index Cond: (end_time_ IS NULL)
									 Filter: (assignee_ IS NULL)
									 Rows Removed by Filter: 512
							   ->  Index Scan using act_idx_hi_ident_link_task on act_hi_identitylink hil  (cost=0.42..9.43 rows=10 width=37) (actual time=0.155..0.155 rows=1 loops=10487)
									 Index Cond: ((task_id_)::text = (res.id_)::text)
									 Filter: ((group_id_ IS NOT NULL) AND ((type_)::text = 'candidate'::text))
									 Rows Removed by Filter: 0
				   ->  Materialize  (cost=0.00..405.43 rows=1 width=36) (actual time=0.000..0.003 rows=1 loops=517)
						 ->  Seq Scan on act_ru_authorization a  (cost=0.00..405.43 rows=1 width=36) (actual time=0.016..1.272 rows=1 loops=1)
							   Filter: ((type_ < 2) AND (resource_type_ = 6) AND (((user_id_)::text = ANY ('{demo,*}'::text[])) OR ((group_id_)::text = 'camunda-admin'::text)) AND ((perms_ & 4096) = 4096))
							   Rows Removed by Filter: 7859
	 Planning time: 11.131 ms
	 Execution time: 832.685 ms