Load test and indy-cli can't connect to the pool after several executions of load test on large pool

Steps to Reproduce:
1. Setup the pool of 7 nodes with 1.2.50 version.
2. Add 18 nodes with 1.2.50 version to the pool.
3. Write ~100 transactions to the pool.
4. Upgrade the pool to 1.3.51 version.
5. Run the load test several times using following command:
for s in `seq 1 2000` ; do python3 Perf_Add_nyms.py -n 500 -s 25 ; done

Actual Results:
About 25800 transactions were successfully written, after that load test freezes on connection to the pool. Indy-cli also can't connect to the pool. But old cli works without any issues.

Expected Result:
Load test and indy-cli should connect to working pool.

Additional Information:
Following action were performed after this problem:

• Remove existing pool and wallet.
• - It didn't help. Pool created, but connection don't work.
• Upgrade libindy to latest master version.
• - After this, load test worked only once. Second time it also freezes on connection to the pool.

Logs with RUST_LOG=indy=trace attached.

This problem blocks load testing on new RC.