I copy-pasted Max combinator and it crashed.

719646.748 Error MainLoop.cpp:1284: Exception at tick 217274104: The mod Useful Combinators (0.5.0) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event UsefulCombinators::on_built_entity (ID 6)
Item is not item-with-tags.
stack traceback:
[C]: in function 'get_tag'
UsefulCombinators/combinators/uc-max-combinator.lua:31: in function 'on_place'
UsefulCombinators/control.lua:50: in function <UsefulCombinators/control.lua:47>
719646.748 Error ServerMultiplayerManager.cpp:92: MultiplayerManager failed: "The mod Useful Combinators (0.5.0) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event UsefulCombinators::on_built_entity (ID 6)
Item is not item-with-tags.
stack traceback:
[C]: in function 'get_tag'
UsefulCombinators/combinators/uc-max-combinator.lua:31: in function 'on_place'
UsefulCombinators/control.lua:50: in function <UsefulCombinators/control.lua:47>"

Will look into

Please fix this . I have same when copy pase

The mod Useful Combinators (0.5.0) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event UsefulCombinators::on_built_entity (ID 6)
Item is not item-with-tags.
stack traceback:
[C]: in function 'get_tag'
...efulCombinators__/combinators/uc-not-gate-combinator.lua:38: in function 'on_place'
UsefulCombinators/control.lua:50: in function <UsefulCombinators/control.lua:47>

seem the error is only in editor mode

Does this happen when the blueprint is placed?

yes.
Now If i'm not in editor mode then I have crash when place a random combinator :

The mod Useful Combinators (0.5.0) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event UsefulCombinators::on_tick (ID 0)
UsefulCombinators/combinators/uc-random-combinator.lua:80: attempt to index field 'parameters' (a nil value)
stack traceback:
UsefulCombinators/combinators/uc-random-combinator.lua:80: in function 'on_tick'
UsefulCombinators/control.lua:82: in function <UsefulCombinators/control.lua:77>

Is the random combinator a blueprint too or the actual item?