LimeSDR fails LimeQuickTest RF loopback test

I was testing the TX capability of my LimeSDR using SDRAngel, when I noticed that my output signal level had suddenly dropped, but was still barely audible. I was transmitting NBFM on VHF with a pigtail antenna connected to TX_1_1, monitoring it using a Yaesu FT-7800 transceiver. First I suspected the settings, but when I switched to TX_2_1 the signal level was OK. To check if anything was wrong I ran LimeQuickTest, it failed in the loopback test with TX_1 CH0 (which is TX_1_1, right?), see output below. Something is clearly wrong with this output, since the signal level is about 30 dB lower than in the other loopback tests. The results are consistent when I re-run the test.

Is my TX_1_1 output pin broken, or could it also be some component in the RF chain between the LMS7002 and th uFL connector? Is there anything I could measure to check what is wrong? Any other tests I could run?

->Start time: Tue Nov 13 21:19:47 2018

->Device: LimeSDR-USB, media=USB 3.0, module=FX3, addr=1d50:6108, serial=0009060B00473622
  Serial Number: 0009060B00473622

[ Clock Network Test ]
->FX3 GPIF clock test
  Test results: 19369; 23125; 26881 - PASSED
->Si5351C test
  CLK0: 17554 / 17554 - PASSED
  CLK1: 17554 / 17554 - PASSED
  CLK2: 17554 / 17554 - PASSED
  CLK3: 17554 / 17554 - PASSED
  CLK4: 17554 / 17554 - PASSED
  CLK5: 17554 / 17554 - PASSED
  CLK6: 17554 / 17554 - PASSED
->ADF4002 Test
  Result: 10 - PASSED
->VCTCXO test
  Results : 5112921 (min); 5113049 (max) - PASSED
->Clock Network Test PASSED

->Read data: 11 01 13 11 01 13 02

[ LMS7002M Test ]
->Perform Registers Test
->External Reset line test
  Reg 0x20: Write value 0xFFFD, Read value 0xFFFD
  Reg 0x20: value after reset 0x0FFFF
->LMS7002M Test PASSED

[ RF Loopback Test ]
->Configure LMS
->Run Tests (TX_2-> LNA_L):
  CH0 (SXR=800.0MHz, SXT=805.0MHz): Result:(-14.8 dBFS, 5.00 MHz) - PASSED
  CH1 (SXR=800.0MHz, SXT=805.0MHz): Result:(-17.4 dBFS, 5.00 MHz) - PASSED
->Run Tests (TX_1 -> LNA_W):
  CH0 (SXR=1800.0MHz, SXT=1805.0MHz): Result:(-56.0 dBFS, 5.00 MHz) - FAILED
  CH1 (SXR=1800.0MHz, SXT=1805.0MHz): Result:(-19.6 dBFS, 5.00 MHz) - PASSED
->Run Tests (TX_2-> LNA_H):
  CH0 (SXR=2500.0MHz, SXT=2505.0MHz): Result:(-16.7 dBFS, 5.00 MHz) - PASSED
  CH1 (SXR=2500.0MHz, SXT=2505.0MHz): Result:(-16.1 dBFS, 5.00 MHz) - PASSED
->RF Loopback Test FAILED

=> Board tests FAILED <=

Elapsed time: 1.51 seconds