In latest version, FTP is constantly reconnecting

I just paid to upgrade from v12 to v13.5 and FTP is now constantly reconnecting. It used to reconnect way more often than it needed to on v12, now its reconnecting constantly.
In v13.5 ANY directory change forces a reconnection, and when I copy over 3 files I get 3 reconnections. I am on a secure system that needs to be reauthorized on each connection, so I have to approve each one, the multiple reconnection requests get stacked up, and frequently the program will get completely messed up and needs to be restarted.

I verified that 'ftp_do_not_cache' is false, which should mean that ftp is caching, and even tried setting setting it to true, but that has no effect.

I went to v13 because I needed newer SSL algorithms, but this is unusable. Please provide a timely fix, or otherwise issue me a refund and I will go back to V12.

What does the FTP log say is happening?

Do other clients work OK on the same server?

FWIW there were no changes to SFTP in the initial vesion of v13, although we do plan to replace the SFTP code completely soon (work has started on that, but I don't know how long it will take yet, especially after discovering there are zero decent SFTP libraries available and we're going to have to make our own, which we've started doing).

First, other FTP clients (smartftp, Mobaxterm) don't have such a problem. And compared to V12, there were changes, (at least) to which key algorithms are available. The reason I upgraded was because I needed newer algorithms for a new server we brought online. And there was an immediate noticeable uptick in reconnections.

This is what the log shows:
Using username "xxxxxx".
Reading key file "xxxxx.ppk"
Using username "moneythu".
Offered public key
Offer of public key accepted
Authenticating with public key "
"
Sent public key signature
Offered public key
Offer of public key accepted
Authenticating with public key "
"
Sent public key signature
Further authentication required
Further authentication required
Further authentication required
Further authentication required
Access granted
Initiating key re-exchange (enabling delayed compression)
Opening session as main channel
Remote debug message: /home/moneythu/.ssh/authorized_keys:7: key options: agent-forwarding port-forwarding pty user-rc x11-forwarding
Remote debug message: /home/moneythu/.ssh/authorized_keys:7: key options: agent-forwarding port-forwarding pty user-rc x11-forwarding
Server supports delayed compression; will try this later
Doing ECDH key exchange with curve Curve25519 and hash SHA-256
Initialised AES-256 SDCTR client->server encryption
Initialised HMAC-SHA-256 client->server MAC algorithm
Initialised zlib (RFC1950) compression
Initialised AES-256 SDCTR server->client encryption
Initialised HMAC-SHA-256 server->client MAC algorithm
Initialised zlib (RFC1950) decompression
Opened main channel
Started a shell/command
SSH: CTS CONNECTED
SSH: Listing Directory
SSH: List complete 17179 files.
SSH: List complete 17179 files.
Access granted
Initiating key re-exchange (enabling delayed compression)
Opening session as main channel
Remote debug message: /home/moneythu/.ssh/authorized_keys:7: key options: agent-forwarding port-forwarding pty user-rc x11-forwarding
Remote debug message: /home/moneythu/.ssh/authorized_keys:7: key options: agent-forwarding port-forwarding pty user-rc x11-forwarding
SSH: List complete 17179 files.
Connection closed
Server supports delayed compression; will try this later
Doing ECDH key exchange with curve Curve25519 and hash SHA-256
Initialised AES-256 SDCTR client->server encryption
Initialised HMAC-SHA-256 client->server MAC algorithm
Initialised zlib (RFC1950) compression
Initialised AES-256 SDCTR server->client encryption
Initialised HMAC-SHA-256 server->client MAC algorithm
Initialised zlib (RFC1950) decompression
Opened main channel
Started a shell/command
SSH: CTS CONNECTED
SSH: Listing Directory
SSH: List complete 17179 files.
Connection closed

Where did you read that?

Unless I've forgotten something, we haven't touched SFTP yet in 13; that's coming in the future.