I created another log file with the iOptronV3 driver, but this time including the debug "verbose scope" option.
Here you can see the command ":GEP#" which is causing repetitive timeout errors at the end. This command is not described in the communication specification you linked in your answer.

INFO 718.730052 sec : Session log file /home/ralf/.indi/logs/2020-06-11/indi_ioptronv3_telescope/indi_ioptronv3_telescope_21:29:59.log
DEBUG 734.337720 sec : Toggle Debug Level -- Scope Verbose
DEBUG 735.273913 sec : Toggle Logging Level -- Scope Verbose
DEBUG 742.177754 sec : Connecting to /dev/ttyUSB0
DEBUG 742.185135 sec : Port FD 4
DEBUG 742.185214 sec : Connection successful, attempting handshake...
DEBUG 742.185285 sec : Initializing IOptron using :MountInfo# CMD...
DEBUG 742.185378 sec : CMD <:MountInfo#>
DEBUG 742.214974 sec : RES <0043>
INFO 742.215092 sec : iOptron v3 is online.
DEBUG 742.240762 sec : Configuration successfully saved for DEVICE_PORT.
DEBUG 742.243339 sec : Configuration successfully saved for DEVICE_BAUD_RATE.
DEBUG 742.249315 sec : Configuration successfully saved for CONNECTION_MODE.
DEBUG 742.255390 sec : Getting firmware data...
DEBUG 742.255436 sec : CMD <:MountInfo#>
DEBUG 742.278902 sec : RES <0043>
DEBUG 742.279073 sec : CMD <:FW1#>
DEBUG 742.310884 sec : RES <191018200113>
DEBUG 742.311006 sec : CMD <:FW2#>
DEBUG 742.342835 sec : RES <190722190722>
DEBUG 742.342979 sec : Getting guiding rate...
DEBUG 742.343004 sec : CMD <:AG#>
DEBUG 742.374791 sec : RES <5050>
DEBUG 742.374921 sec : CMD <:GUT#>
ERROR 747.376227 sec : Read Command Error: Timeout error
DEBUG 747.377197 sec : CMD <:GLS#>
DEBUG 747.402184 sec : RES <+032670500252100521>
INFO 747.402332 sec : Mount Location: Lat -82:59:50 - Long 9:04:30
DEBUG 747.403542 sec : Configuration successfully saved for GEOGRAPHIC_COORD.
INFO 747.435104 sec : Mount is unparked.
DEBUG 747.435425 sec : InitPark Axis1 0.00 Axis2 0.00
DEBUG 747.435467 sec : Setting Default Park Axis1 to 14.88
DEBUG 747.435494 sec : Setting Default Park Axis2 to -90.00
DEBUG 747.435539 sec : CMD <:GLS#>
DEBUG 747.464960 sec : RES <+032670500252100521>
SCOPE 747.465123 sec : CMD <:GEP#>
ERROR 752.469419 sec : Read Command Error: Timeout error
DEBUG 752.470465 sec : CMD <:SUT0645183741000#>
ERROR 757.471040 sec : Read Command Error: Timeout error
DEBUG 757.471716 sec : CMD <:SG+120#>
DEBUG 757.484954 sec : RES <1>
DEBUG 757.485153 sec : CMD <:SLO+03330000#>
DEBUG 757.516935 sec : RES <1>
DEBUG 757.517055 sec : CMD <:SLA+17567892#>
DEBUG 757.548930 sec : RES <1>
INFO 757.549049 sec : Site location updated to Lat 48:47:59 - Long 9:15:00
DEBUG 757.553124 sec : Configuration successfully saved for GEOGRAPHIC_COORD.
DEBUG 757.555690 sec : CMD <:GLS#>
DEBUG 757.581053 sec : RES <+032670500252100511>
SCOPE 757.581231 sec : CMD <:GEP#>
ERROR 762.583778 sec : Read Command Error: Timeout error
DEBUG 763.585888 sec : CMD <:GLS#>
DEBUG 763.615339 sec : RES <+032670500252100521>
SCOPE 763.615620 sec : CMD <:GEP#>
ERROR 768.618495 sec : Read Command Error: Timeout error
DEBUG 769.619793 sec : CMD <:GLS#>
DEBUG 769.648889 sec : RES <+032670500252100521>
SCOPE 769.649136 sec : CMD <:GEP#>
ERROR 774.653449 sec : Read Command Error: Timeout error
DEBUG 775.655608 sec : CMD <:GLS#>
DEBUG 775.683851 sec : RES <+032670500252100521>
SCOPE 775.684024 sec : CMD <:GEP#>
ERROR 780.689158 sec : Read Command Error: Timeout error
DEBUG 781.690959 sec : CMD <:GLS#>
DEBUG 781.717742 sec : RES <+032670500252100521>
SCOPE 781.718000 sec : CMD <:GEP#>
ERROR 786.721690 sec : Read Command Error: Timeout error
DEBUG 787.723204 sec : CMD <:GLS#>
DEBUG 787.752505 sec : RES <+032670500252100521>
SCOPE 787.752750 sec : CMD <:GEP#>
ERROR 792.757422 sec : Read Command Error: Timeout error
INFO 792.762362 sec : iOptron v3 is offline.

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