[TYPO3-Solr] solr, Redis and cache error in Tx_Solr_Template::__construct()

[Jan Slusarczyk]

I am struggling with the following error for the past few months:

On a page with a form and results I cannot enable cache, because any 
pageview other than the 1st (templates being sent to cache) generates 
the following error:

PHP Catchable fatal error:  Argument 1 passed to 
Tx_Solr_Template::__construct() must be an instance of tslib_cObj, 
instance of TYPO3\CMS\Frontend\ContentObject\ContentObjectRenderer 
given, called in 
/var/typo3_src-6.2.7/typo3/sysext/core/Classes/Utility/GeneralUtility.php on 
line 4374 and defined in /typo3conf/ext/solr/Classes/Template.php on line 61

There's no error if the cache is disabled (or the user is logged in BE).

I am using RedisCache and solr is the only extension causing this problem.

I have already asked for help few months ago, and I have mistakenly 
assumed that the problem was caused by a typoscript misconfiguration. 
The only reason this error went away then, was disabling cache for a 
search page...

Any help will be very appreciated because debugging this issue seems to 
be way beyond my knowledge...

Regards
Jan