20 minutes delay in test

With 3.18 there is a 20 minutes delay in the timestamps at one test (11:21:02 → 11:41:23):

$ iperf3 --version
iperf 3.18 (cJSON 1.7.15)
Linux platsch.molgen.mpg.de 5.15.131.mx64.457 #1 SMP Tue Sep 12 12:55:20 CEST 2023 x86_64
Optional features available: CPU affinity setting, IPv6 flow label, TCP congestion algorithm setting, sendfile / zerocopy, socket pacing, authentication, bind to device, support IPv4 don't fragment, POSIX threads
$ iperf3 --server --port 5201 --bind iperf3.molgen.mpg.de --timestamps
[…]
Wed May 14 11:21:02 2025 - - - - - - - - - - - - - - - - - - - - - - - - -
Wed May 14 11:21:02 2025 [ 5] 15.00-16.00 sec 106 MBytes 889 Mbits/sec 204 465 KBytes
Wed May 14 11:21:02 2025 [ 8] 15.00-16.00 sec 96.1 MBytes 806 Mbits/sec 135 433 KBytes
Wed May 14 11:21:02 2025 [ 10] 15.00-16.00 sec 131 MBytes 1.10 Gbits/sec 318 568 KBytes
Wed May 14 11:21:02 2025 [ 12] 15.00-16.00 sec 114 MBytes 953 Mbits/sec 181 445 KBytes
Wed May 14 11:21:02 2025 [ 14] 15.00-16.00 sec 131 MBytes 1.10 Gbits/sec 270 409 KBytes
Wed May 14 11:21:02 2025 [ 16] 15.00-16.00 sec 98.0 MBytes 822 Mbits/sec 122 294 KBytes
Wed May 14 11:41:23 2025 [ 18] 15.00-16.00 sec 44.8 MBytes 375 Mbits/sec 106 177 KBytes
Wed May 14 11:41:23 2025 [ 20] 15.00-16.00 sec 83.0 MBytes 696 Mbits/sec 104 317 KBytes
Wed May 14 11:41:23 2025 [SUM] 15.00-16.00 sec 804 MBytes 6.74 Gbits/sec 1440
Wed May 14 11:41:23 2025 - - - - - - - - - - - - - - - - - - - - - - - - -
Wed May 14 11:41:23 2025 [ 5] 16.00-1236.71 sec 451 MBytes 3.10 Mbits/sec 221 795 KBytes
Wed May 14 11:41:23 2025 [ 8] 16.00-1236.71 sec 432 MBytes 2.97 Mbits/sec 288 775 KBytes
Wed May 14 11:41:23 2025 [ 10] 16.00-1236.71 sec 571 MBytes 3.92 Mbits/sec 316 912 KBytes
Wed May 14 11:41:23 2025 [ 12] 16.00-1236.71 sec 582 MBytes 4.00 Mbits/sec 313 885 KBytes
Wed May 14 11:41:23 2025 [ 14] 16.00-1236.71 sec 556 MBytes 3.82 Mbits/sec 278 857 KBytes
Wed May 14 11:41:23 2025 [ 16] 16.00-1236.71 sec 440 MBytes 3.02 Mbits/sec 410 221 KBytes
Wed May 14 11:41:23 2025 [ 18] 16.00-1236.71 sec 153 MBytes 1.05 Mbits/sec 171 177 KBytes
Wed May 14 11:41:23 2025 [ 20] 16.00-1236.71 sec 420 MBytes 2.89 Mbits/sec 178 317 KBytes
Wed May 14 11:41:23 2025 [SUM] 16.00-1236.71 sec 3.52 GBytes 24.8 Mbits/sec 2175
Wed May 14 11:41:23 2025 - - - - - - - - - - - - - - - - - - - - - - - - -
Wed May 14 11:41:23 2025 [ ID] Interval Transfer Bitrate Retr
Wed May 14 11:41:23 2025 [ 5] 0.00-1236.71 sec 2.06 GBytes 14.3 Mbits/sec 1479 sender
Wed May 14 11:41:23 2025 [ 8] 0.00-1236.71 sec 2.12 GBytes 14.7 Mbits/sec 1223 sender
Wed May 14 11:41:23 2025 [ 10] 0.00-1236.71 sec 2.52 GBytes 17.5 Mbits/sec 2589 sender
Wed May 14 11:41:23 2025 [ 12] 0.00-1236.71 sec 2.45 GBytes 17.0 Mbits/sec 1987 sender
Wed May 14 11:41:23 2025 [ 14] 0.00-1236.71 sec 2.38 GBytes 16.5 Mbits/sec 2115 sender
Wed May 14 11:41:23 2025 [ 16] 0.00-1236.71 sec 2.04 GBytes 14.2 Mbits/sec 1885 sender
Wed May 14 11:41:23 2025 [ 18] 0.00-1236.71 sec 921 MBytes 6.25 Mbits/sec 1068 sender
Wed May 14 11:41:23 2025 [ 20] 0.00-1236.71 sec 1.53 GBytes 10.6 Mbits/sec 821 sender
Wed May 14 11:41:23 2025 [SUM] 0.00-1236.71 sec 16.0 GBytes 111 Mbits/sec 13167 sender
warning: Failed to read JSON data size
Wed May 14 11:41:23 2025 iperf3: error - unable to receive results: Bad file descriptor