ICMP - Yet another destination unreachable - Rookie

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Hi there, I am no Wireshark neither packet capture expert, nevertheless I am attempting to understand why a SIP/TLS app is not behaving as expected, so I have attached wireshark to a mirrored port on our switch, which mirrors all traffic on the PBX network.

What comes to my eyes is that we have some ICMP errors:

No.     Time               Source                Destination           Protocol Length Info                                   DSCP    1056 11:27:32.748536   
172.16.4.10           8.8.8.8               ICMP     174    Destination unreachable (Port unreachable)         Class Selector 6,Default

Frame 1056: 174 bytes on wire (1392 bits), 174 bytes captured (1392 bits) on interface \Device\NPF_{--------HIDDEN----------}, id 0
    Interface id: 0 (\Device\NPF_{--------HIDDEN----------})
    Encapsulation type: Ethernet (1)
    Arrival Time: Apr 16, 2021 11:27:32.748536000 W. Europe Daylight Time
    [Time shift for this packet: 0.000000000 seconds]
    Epoch Time: 1618565252.748536000 seconds
    [Time delta from previous captured frame: 0.000332000 seconds]
    [Time delta from previous displayed frame: 0.000332000 seconds]
    [Time since reference or first frame: 56.350984000 seconds]
    Frame Number: 1056
    Frame Length: 174 bytes (1392 bits)
    Capture Length: 174 bytes (1392 bits)
    [Frame is marked: False]
    [Frame is ignored: False]
    [Protocols in frame: eth:ethertype:ip:icmp:ip:udp:dns]
    [Coloring Rule Name: ICMP errors]
    [Coloring Rule String: icmp.type eq 3 || icmp.type eq 4 || icmp.type eq 5 || icmp.type eq 11 || icmpv6.type eq 1 || icmpv6.type eq 2 || icmpv6.type eq 3 || icmpv6.type eq 4] Ethernet II, Src: Panasoni_yy:yy:yy (xx:xx:xx:xx:xx:xx), Dst: PeplinkI_xx:xx:xx (yy:yy:yy:yy:yy:yy)
    Destination: PeplinkI_xx:xx:xx (yy:yy:yy:yy:yy:yy)
        Address: PeplinkI_xx:xx:xx (yy:yy:yy:yy:yy:yy)
        .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
        .... ...0 .... .... .... .... = IG bit: Individual address (unicast)
    Source: Panasoni_yy:yy:yy (xx:xx:xx:xx:xx:xx)
        Address: Panasoni_yy:yy:yy (xx:xx:xx:xx:xx:xx)
        .... ..0. .... .... .... .... = LG bit: Globally unique address (factory default)
        .... ...0 .... .... .... .... = IG bit: Individual address (unicast)
    Type: IPv4 (0x0800) Internet Protocol Version 4, Src: 172.16.4.10, Dst: 8.8.8.8
    0100 .... = Version: 4
    .... 0101 = Header Length: 20 bytes (5)
    Differentiated Services Field: 0xc0 (DSCP: CS6, ECN: Not-ECT)
        1100 00.. = Differentiated Services Codepoint: Class Selector 6 (48)
        .... ..00 = Explicit Congestion Notification: Not ECN-Capable Transport (0)
    Total Length: 160
    Identification: 0xfaa4 (64164)
    Flags: 0x00
        0... .... = Reserved bit: Not set
        .0.. .... = Don't fragment: Not set
        ..0. .... = More fragments: Not set
    Fragment Offset: 0
    Time to Live: 64
    Protocol: ICMP (1)
    Header Checksum: 0xbece [validation disabled]
    [Header checksum status: Unverified]
    Source Address: 172.16.4.10
    Destination Address: 8.8.8.8 Internet Control Message Protocol
    Type: 3 (Destination unreachable)
    Code: 3 (Port unreachable)
    Checksum: 0xbda8 [correct]
    [Checksum Status: Good]
    Unused: 00000000
    Internet Protocol Version 4, Src: 8.8.8.8, Dst: 172.16.4.10
        0100 .... = Version: 4
        .... 0101 = Header Length: 20 bytes (5)
        Differentiated Services Field: 0x00 (DSCP: CS0, ECN: Not-ECT)
            0000 00.. = Differentiated Services Codepoint: Default (0)
            .... ..00 ...