Not sure as how to tell why it is misusing the line environment.
But the suggested \par solution does not work.

.F


> On 1 Aug 2018, at 21:28, Wolfgang Schuster <wolfgang.schuster.lists@gmail.com> wrote:
> 
> Ending each line in a proper (e.g. by adding \par to finish the paragraph)
> without the misuse the lines environment fixes the problem as well.
> 
> \starttext
> 
> Testing 1971-04-26
> 
> \startcolumns[n=3]
> \dorecurse{200}{+ 17271 \rightarrow\  2018-08-08\par}
> \stopcolumns
> 
> \stoptext
> 
> Wolfgang
> 
> 
> Taco Hoekwater schrieb am 01.08.18 um 13:04:
>> Hi,
>> 
>> Same problem I had.
>> 
>> As a workaround,
>> 
>> \setuplayout[grid=yes]
>> 
>> helps.
>> 
>>> On 1 Aug 2018, at 12:37, Pablo Rodriguez <oinos@gmx.es> wrote:
>>> 
>>> On 08/01/2018 11:48 AM, Henri Menke wrote:
>>>> Cannot reproduce with TL2018 or latest beta.
>>> Hi Henri,
>>> 
>>> I’m afraid that Floris is right. With latest beta and a simple
>>> improvement to your file, I get wrong output:
>>> 
>>>    \starttext
>>>    \startlines
>>>       Testing 1971-04-26
>>>       \startcolumns[n=3]
>>>         \dorecurse{200}{+ 17271 \rightarrow\  2018-08-08
>>>         }
>>>       \stopcolumns
>>>    \stoplines
>>>    \stoptext
>>> 
>>> If the closing parenthesis is on the same line, the plus sign is
>>> misplaced in the last item.
>>> 
>>> With the previous sample, the second page gets a wrong interline space
>>> (between the third and the fourth item from the first column).
>>> 
>>> Pablo
>>> --
>>> http://www.ousia.tk
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>> Taco Hoekwater
>> Elvenkind BV
>> 
>> 
>> 
>> 
>> ___________________________________________________________________________________
>> If your question is of interest to others as well, please add an entry to the Wiki!
>> 
>> maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
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>> archive  : https://bitbucket.org/phg/context-mirror/commits/
>> wiki     : http://contextgarden.net
>> ___________________________________________________________________________________
> 
> ___________________________________________________________________________________
> If your question is of interest to others as well, please add an entry to the Wiki!
> 
> maillist : ntg-context@ntg.nl / http://www.ntg.nl/mailman/listinfo/ntg-context
> webpage  : http://www.pragma-ade.nl / http://context.aanhet.net
> archive  : https://bitbucket.org/phg/context-mirror/commits/
> wiki     : http://contextgarden.net
> ___________________________________________________________________________________