On the old machine that worked;
I started upgrading packages one by one, restarting osmo-bsc, osmo-msc and osmo-mgw each time.
I did that for the following individually, and calls kept working.
apt install osmo-mgw
same apt install for:
osmo-msc
osmo-bsc
libosmo-sigtran5
osmo-stp
libosmocore16
libosmoabis9
libosmotrau2
Then unfortunately I let frustration get the better of my patience, and just went ahead with apt upgrade.
This system is now also giving:
20210219210208350 DCHAN ERROR lchan(0-0-7-TCH_F-0)[0x5568baed4740]{WAIT_BEFORE_RF_RELEASE}: (type=TCH_F) CONNECTION FAIL (cause=Remote Transcoder Failure [ 28 ]) (abis_rsl.c:982)
At least it's confirmed that something in the upgrade broke it:
Reading package lists... Done
Building dependency tree
Reading state information... Done
Calculating upgrade... Done
The following NEW packages will be installed:
linux-headers-4.19.0-14-amd64 linux-headers-4.19.0-14-common linux-image-4.19.0-14-amd64
The following packages will be upgraded:
base-files bind9-host ca-certificates dnsmasq dnsmasq-base file grub-common grub-pc grub-pc-bin grub2-common iproute2 libapache2-mod-php7.3 libasn1c1 libbind9-161
libcairo2 libdns-export1104 libdns1104 libfdt1 libgnutls-dane0 libgnutls-openssl27 libgnutls28-dev libgnutls30 libgnutlsxx28 libisc-export1100 libisc1100 libisccc161
libisccfg163 libldap-2.4-2 libldap-common liblwres161 libmagic-mgc libmagic1 libnode-dev libnode64 libnss-systemd libosmo-e1d-dev libosmo-e1d0 libosmo-gsup-client0
libosmo-mslookup0 libosmo-netif-dev libosmo-ranap3 libosmo-sccp-dev libosmocore-dev libosmocore-utils libosmonetif8 libosmotrau2 libp11-kit-dev libp11-kit0 libpam-systemd
libpq5 libsmpp1 libssl-dev libssl1.1 libsystemd0 libudev1 libzstd1 linux-compiler-gcc-8-x86 linux-headers-amd64 linux-image-amd64 linux-kbuild-4.19 linux-libc-dev
node-ini node-y18n nodejs nodejs-doc openssl osmo-e1d osmo-hlr osmo-sip-connector php7.3 php7.3-cli php7.3-common php7.3-curl php7.3-gd php7.3-intl php7.3-json
php7.3-mbstring php7.3-opcache php7.3-pgsql php7.3-readline php7.3-xml postgresql-9.6 postgresql-client-9.6 postgresql-client-common postgresql-common
postgresql-contrib-9.6 python-apt-common python3-apt sudo systemd systemd-sysv tzdata udev unzip
94 upgraded, 3 newly installed, 0 to remove and 0 not upgraded.
Need to get 107 MB of archives.