IPerf3 showing high TCP packet loss but no UDP?

Have two locations connected by ASE (ATT Circuit) with a 15Mg CIR. Customer is complaining about performance, speedtest consistently shows ~1Mg of throughput. When I run Iperf3 I'm seeing high packet loss for the TCP test but no packet loss for UDP:

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UDP TEST (no packet loss)

Tims-MacBook-Pro:Applications tpfannes$ iperf3 -c 10.208.37.226 -t 120 -i 10 -f m -b 10m -u

Connecting to host 10.208.37.226, port 5201

[ 5] local 10.175.9.82 port 59649 connected to 10.208.37.226 port 5201

[ ID] Interval Transfer Bitrate Total Datagrams

[ 5] 0.00-10.00 sec 11.9 MBytes 10.0 Mbits/sec 8632

….

[ 5] 110.00-120.00 sec 11.9 MBytes 10.0 Mbits/sec 8633

- - - - - - - - - - - - - - - - - - - - - - - - -

[ ID] Interval Transfer Bitrate Jitter Lost/Total Datagrams

[ 5] 0.00-120.00 sec 143 MBytes 10.0 Mbits/sec 0.000 ms 0/103591 (0%) sender

[ 5] 0.00-120.00 sec 143 MBytes 10.0 Mbits/sec 1.137 ms 0/103591 (0%) receiver

​

​

TCP (lotso packet loss)

Tims-MacBook-Pro:Applications tpfannes$ iperf3 -c 10.208.37.226 -t 120 -i 10 -f m -b 10m

Connecting to host 10.208.37.226, port 5201

[ 5] local 10.175.9.82 port 56069 connected to 10.208.37.226 port 5201

[ ID] Interval Transfer Bitrate

[ 5] 0.00-10.00 sec 6.26 MBytes 5.25 Mbits/sec

….

[ 5] 110.00-120.00 sec 4.28 MBytes 3.59 Mbits/sec

- - - - - - - - - - - - - - - - - - - - - - - - -

[ ID] Interval Transfer Bitrate

[ 5] 0.00-120.00 sec 50.7 MBytes 3.54 Mbits/sec sender

[ 5] 0.00-120.00 sec 50.6 MBytes 3.54 Mbits/sec receiver

​

Any suggestions as to why this may be happening? Recommendations for next step? Not sure where to go from here. Thanks!