Please check below log message.
2021-12-14 00:00:04 INFO: [1795d156: pt502 < 45.105.109.125] HEX: bffbff1400405002000a3230303030322e303030
2021-12-14 00:00:04 WARN: [1795d156] error - index: 0, length: -1 (expected: range(0, 821)) - IndexOutOfBoundsException (... < Pt502ProtocolDecoder:160 < ExtendedObjectDecoder:52 < ... < WrapperContext:102 < ...)
2021-12-14 00:00:04 INFO: [1795d156] disconnected
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2021-12-14 00:00:08 INFO: [4da25483: pt502 < 105.34.97.83] HEX: bffbff1400400b02000a3230303030362e303030
2021-12-14 00:00:08 WARN: [4da25483] error - index: 0, length: -1 (expected: range(0, 379)) - IndexOutOfBoundsException (... < Pt502ProtocolDecoder:160 < ExtendedObjectDecoder:52 < ... < WrapperContext:102 < ...)
2021-12-14 00:00:08 INFO: [4da25483] disconnected
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2021-12-14 00:57:58 INFO: [a710e7a8: pt502 < 105.183.114.3] HEX: bffbff3700406402040635352e303030040603333236060406342e30313033080004372e36320900063133302e34300d00014116020135
2021-12-14 00:57:58 WARN: [a710e7a8] error - index: 0, length: -1 (expected: range(0, 54)) - IndexOutOfBoundsException (... < Pt502ProtocolDecoder:160 < ExtendedObjectDecoder:52 < ... < WrapperContext:102 < ...)
2021-12-14 00:57:58 INFO: [a710e7a8] disconnected
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2021-12-14 02:04:23 INFO: [187ea42a: pt502 < 45.101.248.219] HEX: bffbff3800400a0203073432312e3030300407023837060406302e39383839080004352e313709010535352e373814060337303016020136
2021-12-14 02:04:23 WARN: [187ea42a] error - index: 0, length: -1 (expected: range(0, 639)) - IndexOutOfBoundsException (... < Pt502ProtocolDecoder:160 < ExtendedObjectDecoder:52 < ... < WrapperContext:102 < ...)
2021-12-14 02:04:23 INFO: [187ea42a] disconnected
It could mean device issue, protocol change or some server issue. Impossible to tell without looking at the documentation and debugging the samples.
Please check below log message.